Unit 4: Heredity

1

• Unit 4 Heredity
• DNA is comprised of 4 base-pairs
• the purines Adenine and Thymine,
• which join together via 2 H-bonds
• and
• the pyrimidines Guanine and Cytosine
• which join together via 3 H-bonds
• (Review Ch 1 Nucleic Acids)

2

• Unit 4 Heredity
• DNA is comprised of 4 base-pairs
• the purines Adenine and Thymine,
• which join together via 2 H-bonds
• and
• the pyrimidines Guanine and Cytosine
• which join together via 3 H-bonds
• (Review Ch 1 Nucleic Acids)

3

• Unit 4 Heredity
• DNA is comprised of 4 base-pairs
• Adenine and Thymine,
• which join together via 2 H-bonds
• and
• the pyrimidines Guanine and Cytosine
• which join together via 3 H-bonds
• (Review Ch 1 Nucleic Acids)

4

• Unit 4 Hereditary
• DNA is comprised of 4 base-pairs
• the purines Adenine and Thymine,
• which join together via 2 H-bonds
• and
• Guanine and Cytosine
• which join together via 3 H-bonds
• (Review Ch 1 Nucleic Acids)

5
Adenine and Guanine are a class of chemicals
called purines Thymine and Cytosine are a
different class of chemical called pyrimidines
6
Human DNA is approx 3,000 million base pairs in
length (Nearly a metre!) The order of these base
pairs in DNA codes for a vast array of genetic
instructions These instructions vary greatly
in number of base pairs - from 8,000 to
2,000,000! and are called genes 20,000 to
25,000 human genes have so far been
identified Most importantly, a gene (or genes)
is inherited in entirety from one generation to
the next (barring mutation!)
7
Human DNA is approx 3,000 million base pairs in
length The order of these base pairs in DNA
codes for a vast array of genetic
instructions These instructions vary greatly
in number of base pairs - from 8,000 to
2,000,000! and are called genes 20,000 to
25,000 human genes have so far been
identified Most importantly, a gene (or genes)
is inherited in entirety from one generation to
the next (barring mutation!)
8
Human DNA is approx 3,000 million base pairs in
length The order of these base pairs in DNA
codes for a vast array of genetic
instructions These instructions vary greatly
in number of base pairs - from 8,000 to
2,000,000! and are called genes 20,000 to
25,000 human genes have so far been
identified Most importantly, a gene (or genes)
is inherited in entirety from one generation to
the next (barring mutation!)
9
Human DNA is approx 3,000 million base pairs in
length The order of these base pairs in DNA
codes for a vast array of genetic
instructions These instructions vary greatly
in number of base pairs - from 8,000 to
2,000,000! and are called genes 20,000 to
25,000 human genes have been identified Most
importantly, a gene (or genes) is inherited in
entirety from one generation to the next
(barring mutation!)
10
Human DNA is approx 3,000 million base pairs in
length The order of these base pairs in DNA
codes for a vast array of genetic
instructions These instructions vary greatly
in number of base pairs - from 8,000 to
2,000,000! and are called genes 20,000 to
25,000 human genes have been identified Most
importantly, a gene (or genes) is inherited in
entirety from one generation to the next
(barring mutation!)
11
To get a metre of genetic instructions into the
nucleus of every single cell, packaging becomes
very important First the information is ordered
into genes DNA is then twisted the double
helix It is then wrapped around proteins called
histones which are again coiled and super-coiled
into structures called chromosomes Diploid human
cells have 23 pairs of chromosomes, each carrying
a large number of genes 23 pairs 46
chromosomes We get a set of genes from each
parent, hence 23 pairs of chromosomes
12
To get a metre of genetic instructions into the
nucleus of every single cell, packaging becomes
very important First the information is ordered
into genes DNA is then twisted the double
helix It is then wrapped around proteins called
histones which are again coiled and super-coiled
into structures called chromosomes Diploid human
cells have 23 pairs of chromosomes, each carrying
a large number of genes 23 pairs 46
chromosomes We get a set of genes from each
parent, hence 23 pairs of chromosomes
13
To get a metre of genetic instructions into the
nucleus of every single cell, packaging becomes
very important First the information is ordered
into genes DNA is then twisted the double
helix It is then wrapped around proteins called
histones which are again coiled and super-coiled
into structures called chromosomes Diploid human
cells have 23 pairs of chromosomes, each carrying
a large number of genes 23 pairs 46
chromosomes We get a set of genes from each
parent, hence 23 pairs of chromosomes
14
To get a metre of genetic instructions into the
nucleus of every single cell, packaging becomes
very important First the information is ordered
into genes DNA is then twisted the double
helix It is then wrapped around proteins called
histones which are again coiled and super-coiled
into structures called chromosomes Diploid human
cells have 23 pairs of chromosomes, each carrying
a large number of genes 23 pairs 46
chromosomes We get a set of genes from each
parent, hence 23 pairs of chromosomes
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18
To get a metre of genetic instructions into the
nucleus of every single cell, packaging becomes
very important First the information is ordered
into genes DNA is then twisted the double
helix It is then wrapped around proteins called
histones which are again coiled and super-coiled
into structures called chromosomes Diploid human
cells have 23 pairs of chromosomes, each carrying
a large number of genes 23 pairs 46
chromosomes We get a set of genes from each
parent, hence 23 pairs of chromosomes
19
To get a metre of genetic instructions into the
nucleus of every single cell, packaging becomes
very important First the information is ordered
into genes DNA is then twisted the double
helix It is then wrapped around proteins called
histones which are again coiled and super-coiled
into structures called chromosomes Diploid human
cells have 23 pairs of chromosomes, each carrying
a large number of genes 23 pairs 46
chromosomes We get a set of genes from each
parent, hence 23 pairs of chromosomes
20
To get a metre of genetic instructions into the
nucleus of every single cell, packaging becomes
very important First the information is ordered
into genes DNA is then twisted the double
helix It is then wrapped around proteins called
histones which are again coiled and super-coiled
into structures called chromosomes Diploid human
cells have 23 pairs of chromosomes, each carrying
a large number of genes 23 pairs 46
chromosomes We get a set of genes from each
parent, hence 23 pairs of chromosomes
21
Paired chromosomes are joined at a restriction
called a centromere The ends of chromosomes are
called telomeres. To prevent chromosome ends
sticking together they consist of short repeating
DNA sequences TTAGGG in humans Human somatic
cells have 46 chromosomes (somatic cells - all
cells except sperm eggs) This is their diploid
number, written as 2n 46 Human gametic cells
have 23 chromosomes (gametic cells / gametes
sperm eggs) This is their haploid number,
written as n 23
22
Paired chromosomes are joined at a restriction
called a centromere The ends of chromosomes are
called telomeres. To prevent chromosome ends
sticking together they consist of short repeating
DNA sequences TTAGGG in humans Human somatic
cells have 46 chromosomes (somatic cells - all
cells except sperm eggs) This is their diploid
number, written as 2n 46 Human gametic cells
have 23 chromosomes (gametic cells / gametes
sperm eggs) This is their haploid number,
written as n 23
23
Paired chromosomes are joined at a restriction
called a centromere The ends of chromosomes are
called telomeres. To prevent chromosome ends
sticking together they consist of short repeating
DNA sequences TTAGGG in humans Human somatic
cells have 46 chromosomes (somatic cells - all
cells except sperm eggs) This is their diploid
number, written as 2n 46 Human gametic cells
have 23 chromosomes (gametic cells / gametes
sperm eggs) This is their haploid number,
written as n 23
24
Paired chromosomes are joined at a restriction
called a centromere The ends of chromosomes are
called telomeres. To prevent chromosome ends
sticking together they consist of short repeating
DNA sequences TTAGGG in humans Human somatic
cells have 46 chromosomes (somatic cells - all
cells except sperm eggs) This is their diploid
number, written as 2n 46 Human gametic cells
have 23 chromosomes (gametic cells / gametes
sperm eggs) This is their haploid number,
written as n 23
25
Paired chromosomes are joined at a restriction
called a centromere The ends of chromosomes are
called telomeres. To prevent chromosome ends
sticking together they consist of short repeating
DNA sequences TTAGGG in humans Human somatic
cells have 46 chromosomes (somatic cells - all
cells except sperm eggs) This is their diploid
number, written as 2n 46 Human gametic cells
have 23 chromosomes (gametic cells / gametes
sperm eggs) This is their haploid number,
written as n 23
26
Paired chromosomes are joined at a restriction
called a centromere The ends of chromosomes are
called telomeres. To prevent chromosome ends
sticking together they consist of short repeating
DNA sequences TTAGGG in humans Human somatic
cells have 46 chromosomes (somatic cells - all
cells except sperm eggs) This is their diploid
number, written as 2n 46 Human gametic cells
have 23 chromosomes (gametic cells / gametes
sperm eggs) This is their haploid number,
written as n 23
27
Paired chromosomes are joined at a restriction
called a centromere The ends of chromosomes are
called telomeres. To prevent chromosome ends
sticking together they consist of short repeating
DNA sequences TTAGGG in humans Human somatic
cells have 46 chromosomes (somatic cells - all
cells except sperm eggs) This is their diploid
number, written as 2n 46 Human gametic cells
have 23 chromosomes (gametic cells / gametes
sperm eggs) This is their haploid number,
written as n 23
28
Paired chromosomes are joined at a restriction
called a centromere The ends of chromosomes are
called telomeres. To prevent chromosome ends
sticking together they consist of short repeating
DNA sequences TTAGGG in humans Human somatic
cells have 46 chromosomes (somatic cells - all
cells except sperm eggs) This is their diploid
number, written as 2n 46 Human gametic cells
have 23 chromosomes (gametic cells / gametes
sperm eggs) This is their haploid number,
written as n 23
29

• 23 pairs, that is
• 22 pairs of chromosomes and a pair of sex
  chromosomes
• an X Chromosome and a Y Chromosome
• Females have two copies of an X chromosome XX
• Males have one of each chromosome XY
• The 22 pairs of matched chromosomes are called
  autosomes and each can be identified based on
• Size (comparitive)
• Position of the centromeres restriction
• Colour banding variation from chemical staining

30

• 23 pairs, that is
• 22 pairs of chromosomes and a pair of sex
  chromosomes
• an X Chromosome and a Y Chromosome
• Females have two copies of an X chromosome XX
• Males have one of each chromosome XY
• The 22 pairs of matched chromosomes are called
  autosomes and each can be identified based on
• Size (comparitive)
• Position of the centromeres restriction
• Colour banding variation from chemical staining

31

• 23 pairs, that is
• 22 pairs of chromosomes and a pair of sex
  chromosomes
• an X Chromosome and a Y Chromosome
• Females have two copies of an X chromosome XX
• Males have one of each chromosome XY
• The 22 pairs of matched chromosomes are called
  autosomes and each can be identified based on
• Size (comparitive)
• Position of the centromeres restriction
• Colour banding variation from chemical staining

32

• 23 pairs, that is
• 22 pairs of chromosomes and a pair of sex
  chromosomes
• an X Chromosome and a Y Chromosome
• Females have two copies of an X chromosome XX
• Males have one of each chromosome XY
• The 22 pairs of matched chromosomes are called
  autosomes and each can be identified based on
• Size (comparitive)
• Position of the centromeres restriction
• Colour banding variation from chemical staining

33

• 23 pairs, that is
• 22 pairs of chromosomes and a pair of sex
  chromosomes
• an X Chromosome and a Y Chromosome
• Females have two copies of an X chromosome XX
• Males have one of each chromosome XY
• The 22 pairs of matched chromosomes are called
  autosomes and each can be identified based on
• Size (comparitive)
• Position of the centromeres restriction
• Colour banding variation from chemical staining

34

• 23 pairs, that is
• 22 pairs of chromosomes and a pair of sex
  chromosomes
• an X Chromosome and a Y Chromosome
• Females have two copies of an X chromosome XX
• Males have one of each chromosome XY
• The 22 pairs of matched chromosomes are called
  autosomes and each can be identified based on
• Size (comparitive)
• Position of the centromeres restriction
• Colour banding variation from chemical staining

35

• 23 pairs, that is
• 22 pairs of chromosomes and a pair of sex
  chromosomes
• an X Chromosome and a Y Chromosome
• Females have two copies of an X chromosome XX
• Males have one of each chromosome XY
• The 22 pairs of matched chromosomes are called
  autosomes and each can be identified based on
• Size (comparitive)
• Position of the centromeres restriction
• Colour banding variation from chemical staining

36

• 23 pairs, that is
• 22 pairs of chromosomes and a pair of sex
  chromosomes
• an X Chromosome and a Y Chromosome
• Females have two copies of an X chromosome XX
• Males have one of each chromosome XY
• The 22 pairs of matched chromosomes are called
  autosomes and each can be identified based on
• Size (comparitive)
• Position of the centromeres restriction
• Colour banding variation from chemical staining

37
Autosomes are arranged in order by decreasing
size and numbered 1 22 1 being the largest, 22
smallest Members of each chromosome pair match
and are called homologous Non-matching
chromosomes are said to be non-homologous When
visually arranged from 1-22 and sex chromosomes,
referred to as a karyotype A graphical
representation of the karyotype is called an
ideogram
38
Autosomes are arranged in order by decreasing
size and numbered 1 22 1 being the largest, 22
smallest Members of each chromosome pair match
and are called homologous Non-matching
chromosomes are said to be non-homologous When
visually arranged from 1-22 and sex chromosomes,
referred to as a karyotype A graphical
representation of the karyotype is called an
ideogram
39
Autosomes are arranged in order by decreasing
size and numbered 1 22 1 being the largest, 22
smallest Members of each chromosome pair match
and are called homologous Non-matching
chromosomes are said to be non-homologous When
visually arranged from 1-22 and sex chromosomes,
referred to as a karyotype A graphical
representation of the karyotype is called an
ideogram
40
Autosomes are arranged in order by decreasing
size and numbered 1 22 1 being the largest, 22
smallest Members of each chromosome pair match
and are called homologous Non-matching
chromosomes are said to be non-homologous When
visually arranged from 1-22 and sex chromosomes,
referred to as a karyotype A graphical
representation of the karyotype is called an
ideogram
41
Autosomes are arranged in order by decreasing
size and numbered 1 22 1 being the largest, 22
smallest Members of each chromosome pair match
and are called homologous Non-matching
chromosomes are said to be non-homologous When
visually arranged from 1-22 and sex chromosomes,
referred to as a karyotype A graphical
representation of the karyotype is called an
ideogram
42
Autosomes are arranged in order by decreasing
size and numbered 1 22 1 being the largest, 22
smallest Members of each chromosome pair match
and are called homologous Non-matching
chromosomes are said to be non-homologous When
visually arranged from 1-22 and sex chromosomes,
referred to as a karyotype A graphical
representation of the karyotype is called an
ideogram
43
Karyotype
44
Ideogram
45

• During embryonic development, chromosomal errors
  can occur and these are usually fatal
• Errors can include
• Changes in total number of chromosomes
• Changes involving sections of one chromosome
• Changes in the arrangement of chromosomes

46

• During embryonic development, chromosomal errors
  can occur and these are usually fatal
• Errors can include
• Changes in total number of chromosomes
• Changes involving sections of one chromosome
• Changes in the arrangement of chromosomes

47

• During embryonic development, chromosomal errors
  can occur and these are usually fatal
• Errors can include
• Changes in total number of chromosomes
• Changes involving sections of one chromosome
• Changes in the arrangement of chromosomes

48

• During embryonic development, chromosomal errors
  can occur and these are usually fatal
• Errors can include
• Changes in total number of chromosomes
• Changes involving sections of one chromosome
• Changes in the arrangement of chromosomes

49

• During embryonic development, chromosomal errors
  can occur and these are usually fatal
• Errors can include
• Changes in total number of chromosomes
• Changes involving sections of one chromosome
• Changes in the arrangement of chromosomes

50
Changes in total number of chromosomes This can
occur when an extra copy of a gene occurs in a
haploid cell, either sperm or egg, that is
fertilised This results in a total number of 47
chromosomes, 22 pairs and a triplet Down
Syndrome is an example, where 3 copies of
chromosome 21 occur Cells and organisms
(including people) with 3 copies of a chromosome
are called trisomic Monosomy, 1 copy of a gene
(2n 45), results in death, unless involving sex
chromosomes
51
Changes in total number of chromosomes This can
occur when an extra copy of a gene occurs in a
haploid cell, either sperm or egg, that is
fertilised This results in a total number of 47
chromosomes, 22 pairs and a triplet Down
Syndrome is an example, where 3 copies of
chromosome 21 occur Cells and organisms
(including people) with 3 copies of a chromosome
are called trisomic Monosomy, 1 copy of a gene
(2n 45), results in death, unless involving sex
chromosomes
52
Changes in total number of chromosomes This can
occur when an extra copy of a gene occurs in a
haploid cell, either sperm or egg, that is
fertilised This results in a total number of 47
chromosomes, 22 pairs and a triplet Down
Syndrome is an example, where 3 copies of
chromosome 21 occur Cells and organisms
(including people) with 3 copies of a chromosome
are called trisomic Monosomy, 1 copy of a gene
(2n 45), results in death, unless involving sex
chromosomes
53
Changes in total number of chromosomes This can
occur when an extra copy of a gene occurs in a
haploid cell, either sperm or egg, that is
fertilised This results in a total number of 47
chromosomes, 22 pairs and a triplet Down
Syndrome is an example, where 3 copies of
chromosome 21 occur Cells and organisms
(including people) with 3 copies of a chromosome
are called trisomic Monosomy, 1 copy of a gene
(2n 45), results in death, unless involving sex
chromosomes
54
Changes in total number of chromosomes This can
occur when an extra copy of a gene occurs in a
haploid cell, either sperm or egg, that is
fertilised This results in a total number of 47
chromosomes, 22 pairs and a triplet Down
Syndrome is an example, where 3 copies of
chromosome 21 occur Cells and organisms
(including people) with 3 copies of a chromosome
are called trisomic Monosomy, 1 copy of a gene
(2n 45), results in death, unless involving sex
chromosomes
55
Changes in total number of chromosomes This can
occur when an extra copy of a gene occurs in a
haploid cell, either sperm or egg, that is
fertilised This results in a total number of 47
chromosomes, 22 pairs and a triplet Down
Syndrome is an example, where 3 copies of
chromosome 21 occur Cells and organisms
(including people) with 3 copies of a chromosome
are called trisomic Monosomy, 1 copy of a gene
(2n 45), results in death, unless involving sex
chromosomes
56
Changes involving sections of one
chromosome This can occur via deletion of
sections of a chromosome and loss of
genes or Via duplication of sections of a
chromosome and the genes within
57
Changes involving sections of one
chromosome This can occur via deletion of
sections of a chromosome and loss of
genes or Via duplication of sections of a
chromosome and the genes within
58
Changes involving sections of one
chromosome This can occur via deletion of
sections of a chromosome and loss of
genes or Via duplication of sections of a
chromosome and the genes within
59
Changes in the arrangement of chromosomes This
occurs when a section of a chromosome, and subset
of genes, attaches itself to a completely
different chromosome in a process called
translocation