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Regents Biology 14.1 – Human Heredity Originally prepared by Kim B. Foglia Revised and adapted by Nhan A. Pham

14.1 – Human Heredity - Quia · Regents Biology! 14.1 – Human Heredity Originally prepared by Kim B. Foglia Revised and adapted by Nhan A. Pham

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Page 1: 14.1 – Human Heredity - Quia · Regents Biology! 14.1 – Human Heredity Originally prepared by Kim B. Foglia Revised and adapted by Nhan A. Pham

Regents Biology

14.1 – Human Heredity

Originally prepared by Kim B. Foglia Revised and adapted by Nhan A. Pham

Page 2: 14.1 – Human Heredity - Quia · Regents Biology! 14.1 – Human Heredity Originally prepared by Kim B. Foglia Revised and adapted by Nhan A. Pham

Regents Biology

Objectives §  Explain how pedigrees are used to study human

traits. §  Describe examples of the inheritance of human traits. §  Explain how small changes in DNA cause genetic

disorders.

Page 3: 14.1 – Human Heredity - Quia · Regents Biology! 14.1 – Human Heredity Originally prepared by Kim B. Foglia Revised and adapted by Nhan A. Pham

Regents Biology

Human Chromosomes

§  a karyotype §  2 of the 46 human

chromosomes are sex chromosomes.

§  The remaining 44 chromosomes are autosomal chromosomes, or autosomes.

Page 4: 14.1 – Human Heredity - Quia · Regents Biology! 14.1 – Human Heredity Originally prepared by Kim B. Foglia Revised and adapted by Nhan A. Pham

Regents Biology

§  Males and females are born in a roughly 50:50 ratio.

§  Do you know why?

§  … because of the way sex chromosomes segregate during meiosis.

Page 5: 14.1 – Human Heredity - Quia · Regents Biology! 14.1 – Human Heredity Originally prepared by Kim B. Foglia Revised and adapted by Nhan A. Pham

Regents Biology

Human Traits and Pedigrees §  In order to apply

Mendelian genetics to humans, a trait must be: -  controlled by a single

gene -  inherited and NOT

the result of environmental influences

§  A pedigree shows how a trait is passed on from one generation to the next.

Page 6: 14.1 – Human Heredity - Quia · Regents Biology! 14.1 – Human Heredity Originally prepared by Kim B. Foglia Revised and adapted by Nhan A. Pham

Regents Biology

Human Traits and Pedigrees

§  Applications of a pedigree? §  Probability of a child with widow’s peak? With widow’s

peak and attached earlobes?

Page 7: 14.1 – Human Heredity - Quia · Regents Biology! 14.1 – Human Heredity Originally prepared by Kim B. Foglia Revised and adapted by Nhan A. Pham

Regents Biology

Recessively Inherited Disorders §  shows up only in homozygous individuals (aa) §  Many disorders are caused by autosomal recessive

alleles.

Page 8: 14.1 – Human Heredity - Quia · Regents Biology! 14.1 – Human Heredity Originally prepared by Kim B. Foglia Revised and adapted by Nhan A. Pham

Regents Biology

Recessively Inherited Disorders

http://www.youtube.com/watch?v=l0dDhKFk2HU

Page 9: 14.1 – Human Heredity - Quia · Regents Biology! 14.1 – Human Heredity Originally prepared by Kim B. Foglia Revised and adapted by Nhan A. Pham

Regents Biology

Dominantly Inherited Disorders §  expressed even when

the recessive allele is present

§  Many are caused by autosomal dominant alleles.

Page 10: 14.1 – Human Heredity - Quia · Regents Biology! 14.1 – Human Heredity Originally prepared by Kim B. Foglia Revised and adapted by Nhan A. Pham

Regents Biology

From Gene to Molecule §  An allele responsible for

a genetic disorder codes for: -  a malfunctioning

protein or -  no protein at all

§  Such changes are due to small changes in the DNA.

§  In CF, 3 bases missing à no phenylalanine (Phe)

Page 11: 14.1 – Human Heredity - Quia · Regents Biology! 14.1 – Human Heredity Originally prepared by Kim B. Foglia Revised and adapted by Nhan A. Pham

Regents Biology

§  predominant in African Americans (1 in 400)

§  3 phenotypes -  SS (sickle cell

anemia) -  Ss (resistance to

malaria) Heterozygote advantage

-  ss (normal) §  Codominant?

Sickle Cell Disease

http://www.youtube.com/watch?v=Qd0HrY2NlwY

Page 12: 14.1 – Human Heredity - Quia · Regents Biology! 14.1 – Human Heredity Originally prepared by Kim B. Foglia Revised and adapted by Nhan A. Pham

Regents Biology

Heterozygote Advantage

Regions where malaria is common Regions where the sickle cell allele is common

Page 13: 14.1 – Human Heredity - Quia · Regents Biology! 14.1 – Human Heredity Originally prepared by Kim B. Foglia Revised and adapted by Nhan A. Pham

Regents Biology

Dominant ≠ most common allele

Polydactyly

§  Because an allele is dominant does not mean… -  it is better, or -  it is more common

Page 14: 14.1 – Human Heredity - Quia · Regents Biology! 14.1 – Human Heredity Originally prepared by Kim B. Foglia Revised and adapted by Nhan A. Pham

Regents Biology

Polydactyly §  The allele for >5 fingers/

toes is dominant. §  The allele of 5 digits is

recessive. § Recessive alleles are far

more common than dominant.

§ Only 1 individual out of 500 has more than 5 fingers toes (499 out of 500 people are homozygous recessive (aa))

Page 15: 14.1 – Human Heredity - Quia · Regents Biology! 14.1 – Human Heredity Originally prepared by Kim B. Foglia Revised and adapted by Nhan A. Pham

Regents Biology

Hound Dog Taylor