Intro to Genetics

Question 1

Genetics come from DNA

Question 2

Chromosome Traits

Answer 2

• Located in nucleus of cells
• Long chains of DNA
• Carry info for lots of traits
• Individual bits of info, are called genes
• Number (per cell) varies between species
• Exist in pairs in somatic (body) cells

Question 3

Number of Chromosomes

Answer 3

• Humans 46 (23 prs)
• Cats 38 (19 prs)
• 46 is the diploid number
• 23 is the haploid number
• 44 (36 for cats) are autosomes
• 2 are sex chromosomes

Question 4

Sex Chromosomes

Answer 4

• Female is XX
• Male is XY
• Y is much smaller, carries little info
• Reversed in birds

Y chromosomes are small and usually don’t carry an allele
* SO, males will only have one copy of a sex-linked gene
* Females will have 2

Question 5

Genes

Answer 5

Different forms (of same gene) are called alleles:
* Small parts of chromosomes
* Control one specific trait or part of a trait
* May be in different forms on the pair of chromosomes

Question 6

Gametes (Sperm and Eggs)

Answer 6

• Are haploid
• Only contain 1 copy of each chromosome
• Random (50/50 chance) of which one it contains
• Can then only contain an X or a Y chromosome

Question 7

Symbolize Genes with Letters

Answer 7

• Alleles of a gene will have the same letter
• If more than 2 alleles exist for a gene, we will use superscripts

Question 8

If we know:
* Dominance relationship of alleles
* Genotypes of parents (sire and dam)

We can predict:
* Expected phenotype of offspring

Question 9

Red-green color blindness

Answer 9

• Example of a sex-linked trait
• “Normal” vision (ability to see colors) is dominant to color-blindness
• Cross a male with normal vision with a female with normal vision, but who is heterozygous (often called a “carrier”)

Question 10

HOW CAN WE GET A COLOR-BLIND FEMALE?

Answer 10

• the father must be color blind and the mother must be a carrier or be color-blind
• A father can’t pass color blindness to his son because he has to pass the Y chromosome