Human Genetics

1
Human Genetics
2
Human Genome Project

• Many human traits follow the patterns explained
  by Mendelsome do not.
• Most people think that dominant is better and
  that dominant genes are more frequently found
• Scientists are currently doing research to figure
  out human genetics
• Problems
• Humans more complicated than simpler organisms
• Longer time periods between generations
• Families are too small for genetic study
• Unethical to carry out breeding experiments in
  humans
• Scientists came up with the Human Genome Project
• Finished in 2003 to identify the 20-25,000 genes
  of human DNA and to determine the 3 billion base
  pairs that make up your DNA

3
Personal Genetic Profiles

• Many of your traits obey Mendels principles
• Fill in Table 7-1 on pg. 84
• Figure 7-1 on pg. 85 shows you different traits
• PTC tasting
• If you taste anything, you are a taster if not
  you are a non-taster
• The taster allele (T) is dominant
• Tongue rolling roller (R) is dominant
• Interlocking fingers left (L) is dominant
• Hitchhikers thumb Straight (S) is dominant
• Widows Peak widows peak (W) is dominant
• Bent pinky finger bent finger (B) is dominant
• Free ear lobes free (F) is dominant
• Are dominant traits more common than recessive?

4
Sex Chromosomes

• In humans, sex of a child is determined by the
  sex chromosomes
• Men have XY
• Women have XX
• This means that men determine the sex of a child
• Complete the Punnett Square to the right to
  answer the questions for Activity 3 on pg. 88

Mom
XX
X
X
Y
XY
Dad
X
5
Sex-linked traits

• Sex-linked traits are traits controlled by genes
  that are located on the sex chromosomes
• Since the Y chromosome only carries three genes,
  when you talk about sex-linked traits you are
  talking about traits carried on the X chromosome
• Activity 4 pg. 89 Color-blindness is an X-linked
  trait
• The allele for color-blindness is recessive (b)
  and the allele for normal sight is dominant (B)
• Therefore, a color-blind male is symbolized by
  XbY and a female by XbXb
• A normal male would be XBY and a normal female
  XBXB
• If a normal male marries a color-blind female
  what would the expected phenotypes of their
  children be?
• For X-linked traitsthe boys are screwed!

6
Sex-linked traits

• Problem B of Activity 4
• Muscular dystrophy (MD) is caused by an X-linked
  recessive gene (d)
• Two normal individuals marry and have a son who
  develops muscular dystrophy
• Give the genotypes of the parents
• Mom is XDXd and Dad is XDY
• Could these parents have a daughter with muscular
  dystrophy?
• No-b/c you get one chromosome from mom (XD or Xd)
  and one from Dad (only has XD) no matter which
  one she gets from Mom, she can only get a normal
  X from Dad and show no recessive gene
• BUT she is a carrier and her sons may show MD

7
Blood typing

• For the traits that Mendel worked with, there
  were two forms of each allele in a population
  (dominant and recessive)
• Not all genes follow that pattern (red
  snapdragons white snapdragons pink
  snapdragons)
• For some traits, there are more than 2 forms of
  the gene in the population
• Ex Blood typing of ABO blood group
• Has three alleles instead of two (IA, IB, and
  i)but you still only possess two! It just
  depends on what two you get from your parents
• Has co-dominance (A is co-dominant with B)

8
Blood typing

• Your red blood cells have molecules called
  antigens on the outside surface of the cell (A or
  B)
• Antibodies (germ fighting molecules) can bind to
  the A or B antigens on the outside of the red
  blood cell and cause them to stick and clump
  together (agglutinate)
• Whatever antigen you have, antibodies for that
  antigen will cause your red blood cells to
  agglutinate
• So.

9
Blood typing
10
Whos kid are you?

• Andrea and John are married with one kid Marline
• Andrea and John die and leave their fortune to
  Marline in their will
• Daryl claims to be a child of Andrea and Johns
  and therefore entitled to half the fortune?
• Is Daryl their son?

11
Karyotype

• Karyotype refers to the chromosomal make-up of
  the body cells of an individual
• Humans have 23 pairs of chromosomes (one from mom
  and one from dad)
• A karyotype is the picture of these chromosomes
• Pg. 92 shows a picture of a normal males
  chromosomes
• They are numbered 1-23 and arranged by position
  of the centromere
• Notice how each rows chromosomes are shorter
  than the one above it---KNOW THIS FOR YOUR QUIZ
  NEXT WEEK!
• Can do this with a baby to see any abnormal
  chromosome pairing (Remember non-disjunction
  disorders from last week)

12
Karyotype

• How is a normal womans karyotype different than
  a normal males karyotype?
• Non-disjunction isnt the only cause of
  abnormalities
• Deletion missing part of a chromosome
• Translocation part of one chromosome joined to
  another chromosome

13
Karyotypes

• What is wrong with these karyotypes?

14
Homework

• Pg. 99 1, 2, 3, and 6
• For 6 1 normal karyotype (male or female) and 1
  karyotype of a male with Down Syndrome