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Chapter 26: Genetics. Genes and chromosomes. Eye color. Hair color. Skin color. Nose size. Nose shape. Genes. Eye shape. hair texture. Ear size. widow’s peak. Ear lobes. Chromosome. Types of Chromosomes. Sex Cell. Body Cell. Chromosomes NOT paired. - PowerPoint PPT Presentation
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Genes and chromosomes
Chromosome
Genes
Eye color
Hair color
Skin color
Nose size
Nose shape
Eye shape
hair texture
Ear size
widow’s peak
Ear lobes
Types of Chromosomes.
Sex Cell Body Cell
Chromosomes are paired and therefore have two genes for every trait
Chromosomes NOT paired
A body cell has ___________ genes for every trait.
Sex cells only have ________ gene for every trait
two
One
B = b =
Child has a gene for BLUE eyes and a gene for BROWN eyes…
????
B b
B b
Brown eyed Dad Blue eyed Mom
What happens when you have a gene for Brown eyes AND a gene for Blue eyes??
A gene that will SHOW the trait
A gene that will NOT show the trait if a dominant gene is present.
B B = ___________________
B b = ___________________
b b =
Brown eyes
Brown eyes
Blue eyes
Terminology:
= HOMOZYGOUS Dominant
(pure dominant)
= HETEROZYGOUS
(hybrid)
= HOMOZYGOUS recessive
(pure recessive)
GENOTYPE – a person’s genes PHENOTYPE (physical appearance)
Brown eyes
Brown eyes
Blue eyes
Punnett SquareA method for predicting the possible outcomes (offspring) of a genetic cross
Mother’s Genes
Father’s
Genes
B b
B
b
B B
B b
B b
b b
Gregor Mendel: 1865
• Austrian monk
•Father of genetics
• Botanist
• Worked with pea plants.
• Discovered recessive and dominant genes using mathematics
•Genetics – study of how traits are passed from parent to offspring
Mendel’s experiments:G G
g
g
GG gg
G g
G
g
Gg Gg
Gg Gg
GG Gg
Gg gg
yellow Yellow yellow green
P1
F1
F2
All yellow
* green trait “disappeared”??
3 yellow
1 green
*green trait “re-appeared”
Mendel repeated this for all the traits of a pea plant. Since the results were the same, he concluded:
Mendel used statistics and punnett squares to accurately predict the outcomes of all his possible genetic crosses.
TT x TT = all tall
TT x Tt = all tall
Tt x Tt = ¾ tall, ¼ short
Tt x tt = ½ tall, ½ short
TT x tt = all tall
tt x tt = all short