1. Human Genetics 1

2. Studying Human Inheritance
The Human Genome
Genome – all the genes in an organism
Roughly 19, ,000 genes in a human
Geneticists can trace the passage of genes in families
Disease-causing genes are easily traced from one generation to the next
Families may pursue genetic counseling if they feel at risk for passing a disease to a child.

3. Vocabulary Reminder…
Autosome: a chromosome that does not determine gender
Humans have 22 pairs of autosomes (44 total)
An autosomal trait is carried on an autosome
Sex Chromosome: a chromosome that determines gender
Humans have 2 sex chromosomes (1 pair)
Women are XX
Men are XY

4. Genetic Disorders
Genetic Disorder – debilitating condition with a genetic basis
Autosomal Dominant Disorders – disease is passed by inheritance of at least 1 dominant allele (Aa or AA)
Autosomal Recessive Disorders – disease is passed by inheriting 2 recessive alleles (aa)
Sex-Linked Trait or Disorder – disease or trait located on the X Chromosome (XNXN, XNXn,XnXn, XNY, or XnY)

5. Some Autosomal Dominant Genetic Disorders
Huntington’s Disease
Autosomal Dominant
Symptoms (irritability & forgetfulness) do not show for years
Advanced Symptoms
Loss of muscle control
Physical spasms
Mental illness
Eventual death
Person is not aware of disease until an adult
Achondroplasia
Autosomal Dominant
“Dwarfism”
Affected are short in stature with disproportionate arm and leg lengths
Health problems include obesity, back problems, and increased mortality between yrs. Old
Growth Hormone therapy speeds up growth in children.

6. Some Autosomal Recessive Genetic Disorders
Albinism
Autosomal Recessive
Phenotype is lighter hair, skin, and eyes
Affected fail to produce enough melanin
Other health issues include
Blindness
Jerky Eye Movement
Risk of skin cancer
Cystic Fibrosis
Autosomal Recessive
Affects the respiratory, digestive, and reproductive tracts
Causes secretions like mucous, sweat, or digestive juices to clog up body passages
No cure; can use gene therapy for some relief
Lifespan up to yrs.

7. Another Vocabulary Review
Heterozygous: a genotype having one dominant and one recessive allele for a trait
Ex: Aa or Bb or Dd
Homozygous: a genotype having either two same dominant or two same recessive alleles for a trait
Ex: AA or aa or GG or gg

8. The Pedigree
A family tree chart used to trace the passage of a disease through a bloodline

9. Pedigree Basics
Men are usually symbolized w/a square & women with a circle.
If one is homozygous for a trait under investigation then the shape is colored in.
If one is heterozygous for a trait & the dominant trait is the one focused on in the pedigree then a shape is colored in.
Carriers are half colored in
Carrier – a person with a dominant phenotype but having a heterozygous genotype (Aa) that “carries” a recessive allele that could be passed on.

10. You Draw the Pedigree
Create a pedigree for a heterozygous man whose dad has albinism
The man marries a woman who is homozygous normal.
They have 3 kids, 2 girls and a boy.
The youngest girl carries the albinism allele

11. You Draw the Pedigree 2
Create a pedigree for a man whose mom is an achondroplasiac dwarf.
The man is also a dwarf, though his dad is of normal height.
The man marries a woman who is normal.
They have 3 kids, 2 girls and a boy.
The middle girl is a dwarf.