1. Human Genome
Biology Ch 14

2. Chromosomes Carries genetic information from parents to offspring
Karyotype – picture of all
chromosomes grouped in pairs
Autosomes – chromosomes paired together by size, shape, content (22 pairs)
Sex Chromosomes – one pair of chromosomes that determine gender (one pair)

3. Sex Chromosomes
XX = Female
XY = Male

4. Pedigree
Can use genetic information to develop a pedigree – a chart that shows traits as passed from generation to generation
P = Parent generation
F1 = First offspring generation
F2 = next generation offspring

5. Pedigree Problem
Imagine that you are a genetic counselor. The pedigree shown on the next slide illustrates the inheritance of albinism in three generations of a family. A couple from the family have come to you to ask for advice about how the trait is inherited.
*Your task is to determine whether the allele for albinism is dominant or recessive.*

6. Pedigree Problem Answer on a separate piece of paper:
By remembering the previous slide, restate the problem that must be solved.
Copy this pedigree on to the paper. Label each person on the pedigree with his or her phenotype: normal (N) or albino (A).
Write down HOW you would analyze the pattern of inheritance of the albinism trait and describe how you will use your analysis to infer the genotype of as many individuals as possible.

7. Trait Control Most human traits are NOT controlled by a single gene
Other controls:
Multiple genes – polygenic
Environmental
influence
Single gene trait

8. Multiple Controls Blood type = CoDominance & Multiple Alleles
IA, IB, I
IA and IB are Co-dominant AND are BOTH dominant over the recessive i
Genotype(s)
IAIA , IA i
IBIB, IBi
IAIB ii

9. Polygenic trait distribution
Polygenic traits give a bell curve shaped distribution, whereas single gene traits will show an “all-or-nothing” bar graph.
Single gene trait distribution graph:

10. Can be single gene mutation or polygenic mutation)
Autosomal Chromosome disorders
Mutations found ONLY on the autosomes (chromosomes 1 through 22)
Can be single gene mutation or polygenic mutation)
Autosomal Dominant Genetic Disorders:
These disorders are caused when an individual has inherited the defective allele from a single parent. Ex: Aa or AA (Dwarfism, Huntington disease)
Autosomal Recessive Genetic Disorders: Such disorders manifest only when an individual has got two defective alleles of the same gene, one from each parent. Ex: aa (Albinism, Cvstic fibrosis)
Co-dominant alleles:
Disorder manifested when two dominant alleles are inherited. Ex: AB (Sickle cell disease)
Multi-factorial Genetic Disorders: Such disorders are the result of genetic as well as environmental factors. (Alzheimer’s disease?, dementia?)

11. Sex linked genes Genes found X or Y chromosomes
X chromosome has approx 1000 genes – Many life functions
Y chromosome have approx 150 genes – SRY region determines male characteristics
Sex-linked traits:
Colorblindness
Hemophilia
Duchenne Muscular Dystrophy

12. Autosome Chromosome Disorders
Non-disjunction – results in abnormal number of chromosomes in gametes (Down Syndrome)
Sex Chromosome Disorders