Inheritance of Traits

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Inheritance of Traits

• Biology 2

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How Genetics Work

• Genetics is the study of how traits are passed
  for parents to offspring
• We learned about chromosomes
• They are found in the nucleus
• They are made of DNA
• Humans have 46 chromosomes, but only 23 in the
  sex cells

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How Genetics Work

• More about chromosomes
• All chromosomes contain genes
• Genes are small sections that determine specific
  traits
• Traits could be eye color, hair color, skin
  color, etc
• In the body cells, the chromosomes are pair so
  there are 23 pairs or 46 total
• In the sex cells, the chromosomes are single so
  there are only 23 total

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Chromosomes
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How Genetics Work
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How Genetics Work

• Traits are passed from parents to offspring
• Genotype vs. Phenotype
• Genotype is the genetic make of the organism
• Phenotype is what the organism looks like
• How can an offspring have characteristics that
  neither parent have?
• Because not all genes are expressed some are
  carried by the parents and expressed in the
  offspring

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How Genetics Work

• Dominant Traits
• Genes that keep other genes from showing
• An organism with two dominant genes is homozygous
  dominant the trait is expressed
• An organism with one dominant trait and one
  recessive trait is heterozygous the trait is
  still expressed

• Recessive Traits
• Genes that do not show when dominant traits are
  present
• The only way for these traits to be expressed is
  when 2 recessive genes are present
• This is called homozygous recessive

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Punnett Squares

• Punnett Squares are used to predict the phenotype
  based off the genotype
• Uppercase letters will be used for all dominant
  genes are lowercase letters will be used for all
  recessive genes
• Remember each gene has a pair and the pair is
  either going to be homozygous or heterozygous

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Punnett Squares

• Setting up Punnett Squares Step 1 draw a box
  with 4 squares

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Punnett Squares

• Step 2 on the top and side of the box write the
  parents genotype

f
f
F
f
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Punnett Squares

• Step 3 match up the top and side in each box
  inside the square

f
f
F
Ff
Ff
ff
ff
f
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Punnett Square

• Step 4 Analyze the results
• Lets say the F stands for freckles
• The father has a genotype Ff What is his
  phenotype?
• The mother has a genotype ff what is her
  phenotype?
• The possible combinations of the offspring are Ff
  or ff what could their phenotypes be?

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Punnett Squares
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Punnett Squares

• Punnett Squares were developed by Gregor Mendel
• He is said to be the father of genetics
• He noticed that pea plants had a variety of
  features and when he crossed them he got
  different results
• He developed the concept of dominant and
  recessive genes

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Human Genetics

• There are a total of 46 chromosomes in each human
  body cell
• 23 pairs 23 from the mother and 23 from the
  father
• 1 pair determines the sex of the offspring
  these are called sex chromosomes
• The other 22 pairs are called autosomes

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Human Genetics
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Human Genetics

• Determining sex using Punnett squares

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Human Genetics

• Blood type is also determined by genetics
• OO is recessive
• A B are dominant
• Combinations AO, AA, BO, BB, AB, OO

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Genetic Disorders

• What happens when something goes wrong in the
  genes?
• A genetic disorder can occur
• Some disorders are minor and can easily be lived
  with however, others are fatal

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Genetic Disordershttp//www.noah-health.org/en/ge
netic/

• Disorders of the Sex Chromosomes
• Hemophilia blood disorder where the blood wont
  clot
• XXX syndrome many dont have signs or symptoms,
  but some can include delayed puberty,
  infertility, mental retardation (extreme cases)
  occurs only in females
• XXY syndrome learning disablities, lower IQs
  occurs only in boys

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Genetic Disordershttp//www.noah-health.org/en/ge
netic/

• Disorders of the Sex Chromosomes
• Turners Syndrome girls born without the other X
  chromosome without treatment girls will not
  grow to full height or reach puberty

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Genetic Disordershttp//www.noah-health.org/en/ge
netic/

• Other Disorders
• Albinism
• Color-blindness
• Cystic Fibrosis
• Down Syndrome
• Fragile X Syndrome
• Huntingtons Disease
• Klinefelter Syndrome