7.4 Human Genetics and Pedigrees SPONGE 4 What is the difference between incomplete dominance and...

7.4 Human Genetics and Pedigrees

SPONGE 4

What is the difference between incomplete dominance and codominance? (7.2)

• Give an example of each


• In incomplete dominance, neither allele is completely dominant nor completely recessive.

Codominant alleles will both be completely expressed.

+ =

The flower will show both red and white

+ =

7.4 Human Genetics and PedigreesSet up Cornell Notes on pg. 91•Topic: 7.4 Human Genetics and Pedigrees

•Essential Questions:

•Don’t forget to add it to your T.O.Contents!

2.1 Atoms, Ions, and Molecules



KEY CONCEPT A combination of methods is used to study human genetics.


• The basic principles of genetics are the same in all sexually reproducing organisms.

– Inheritance of many humantraits is complex.

– Single-gene traits areimportant in understandinghuman genetics.

Ex: widow’s peak

Widow’s peak


Females can carry sex-linked genetic disorders.

• Males (XY) express all of their sex linked genes.• Expression of the disorder depends on which parent carries

the allele and the sex of the child.

XY


A pedigree is a chart for tracing genes in a family.

• Phenotypes are used to infer genotypes• Autosomal genes show different patterns on a pedigree

than sex-linked genes.

Widow’s peak

No Widow’s peak


Boxes = malesCircles = females Shaded = they show the traitWhite = does not show traitHalf shaded = carrier


1. How many females are in this family?2. How many carriers?3. How many children were in generation two?4. How many offspring in generation three are affected by the trait?

Generation 1

Generation 2

Generation 3

Generation 4


Sponge 61.How many females are in this family? 112.How many carriers? 73.How many children were in generation two? 54.How many offspring in generation three are affected by the trait? 2

Generation 1

Generation 2

Generation 3

Generation 4


• If the phenotype is more common in males, the gene is likely sex-linked (meaning the trait is on the X chromosome). Ex: Color blindness

males

females


Please draw a pedigree chart:

Mary and Joe were married in 1912.

Joe had a Widow’s Peak (Ww) which is dominant, while Mary did not have a Widow’s Peak (ww)

They had two children: A son named Pete who had a Widow’s Peak and a girl named Isabel who did not have a Widow’s Peak.

Pete married a woman who was homozygous for a Widow’s Peak (WW), but their daughter Isabel never married.

Pete and his wife had three boys.

Do his boys have Widow’s Peaks?


Joe Mary

Pete Isabel

Ww ww

Ww wwWW


• A karyotype is a picture of all chromosomes in a cell.

X Y


• Karyotypes can show changes in chromosomes.

– deletion of part of a chromosome or loss of a chromosome

– large changes in chromosomes– extra chromosomes or duplication of part of a

chromosome


• In down syndrome a person has an extra copy of chromosome 21.

• In Klinefelter’s syndrome a male has an extra X (XXY).

7.4 Human Genetics and Pedigrees SPONGE 4 What is the difference between incomplete dominance and...

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