1. Bellwork questions: answer these in your notebooks (you may use your text)
what are autosomes?
What are sex chromosomes?
What are the human autosomes and sex chromosomes?
What are the chances of two parents conceiving a boy? A girl?

2. Ch 12 Inheritance patterns and Human Genetics

3. Human chromosome review
23 pairs
1-22 = autosomes
23rd pair = sex chromosome
What are they two sex chromosomes?
Female: XX
Male: XY
Y chromosome contains SRY gene
SRY: Sex determining Region Y- gene coding for production of male gonads (testes)

4. Sex-linked genes and traits
Sex-linked traits: trait coded for by alleles on a sex chromosome
X chromosome much larger = many more gene than Y
Examples:
SRY (Y-linked)
Color blindness (X-linked)
Hemophilia (x-linked)

5. Linked genes
Linked genes: pairs of genes that tend to be inherited together
Genes close to each other on chromosome
Example
If crossing over occurs, A & B are likely to be inherited together
A & E less likely

6. Mutations Change in nucleotide base sequence
Germ cell mutation: in gametes
does not affect organism
can be passed down to offspring
Somatic cell mutation: in body cells
Can affect organism
Lethal mutations: can cause death (usually before birth)

7. Mutations Chromosomes can be: DNA bases (& sequences) can be: Deleted
Flipped around (inverted)
Moved to the wrong chromosome
DNA bases (& sequences) can be:
Inserted
Substituted
Etc.

8. Mutations Two main categories: Chromosomal (affect chromosome)
Nondisjunction: chromosomes fail to separate during meiosis
Down Syndrome

9. 2. Gene (affect DNA sequence)
Frameshift: affects one codon and as a result, all codons downstream are changed (shifts the reading frame
ATC/GTA/GCT/GCT/ATT
ATC/GTT/AGC/TGC/TAT/T

10. Chromosomal
Nondisjunction video

11. Gene

12. 12-2 Human genetics
Pedigree: diagram that shows how a trait is inherited over several generations

13. Pedigrees used to: see patterns of inheritance
See if trait is autosomal or sex-linked
Dominant or recessive

14. Genetic traits and disorders
Some traits have a single gene with two or more alleles
Blood type
Cystic fibrosis
Most human traits are polygenic: characters influenced by several genes
Skin color; 3-6 genes

15. Genetic traits and disorders
Complex characters: influenced by environment and genes
Skin color exposed to sunlight
Height
Breast cancer
Diabetes
Heart disease

16. Multiple alleles
Genes have more than three alleles
ABO blood type

17. Incomplete dominance
Heterozygote is an intermediate phenotype

18. X-linked traits More common in males (x-linked recessive)
Males inherit X from mom and no other
No possibility of heterozygous
colorblindness

19. Single allele traits Single allele of a gene controls these traits
<200 human traits
Huntington’s Disease
Autosomal dominant
y. o.

20. Detecting genetic disease
Genetic screening: examination of a person’s genetic information
Need DNA from embryo
Amniocentesis: removal of amniotic fluid surrounding fetus
14th-15th week
Chorionic villi sampling: sample of chorion villi (tissue surrounding developing embry)
8th-10th week

22. Open text to page 246 Copy table in your notes
You only need the disorder, pattern of inheritance, and brief description of symptoms