Punnett Squares and Pedigrees

Question 1

Chromosomes

Answer 1

Contain genes that codes for a particular trait –>
Genes can come in more than one form called alleles

Question 2

Complete Dominance

Answer 2

Occurs when dominant allele completely masks expression of the other allele (what Gregor Mendel looked at with pea plants)

Question 3

Dominant vs Recessive

Answer 3

Alleles can either be dominant or recessive; dominant alleles prevent the expression of a recessive allele (in complete dominance) –> capital letters = dominant, lowercase = recessive

Question 4

Heterozygous vs Homozygous

Answer 4

Heterozygous: two different alleles (ie. one dominant and one recessive)
Homozygous: two of same alleles (ie. both dominant/both recessive)

Question 5

Genotype

Answer 5

Genetic makeup of alleles, the combo of alleles for any given trait (eg. BB, bb, or Bb)

Question 6

Phenotype

Answer 6

The physical and psychological traits of an organism (eg. purple flowers or white flowers)

Question 7

Generations

Answer 7

Parent generation crosses to form F1 generation, F1 generation crosses to form F2 generation

Question 8

Law of Independent Assortment

Answer 8

If genes are located on separate chromosomes, they are inherited independently of each other (dihybrid crosses)

Question 9

Incomplete Dominance

Answer 9

Neither allele is dominant so a blending/mix of the traits is expressed (ie. red allele + white allele = pink)

Question 10

Codominance

Answer 10

Both alleles may be dominant therefore both are fully expressed

Question 11

ABO Blood Groups

Answer 11

4 major blood types: A, B, AB, O
3 alleles for blood type: Iᴬ, Iᴮ, i (i is recessive, Iᴬ and Iᴮ are codominant)
Type AB: universal recipient
Type O: universal donor

Question 12

Antigens and Antibodies

Answer 12

Antigens are genetically determined proteins found on the plasma membrane of red blood cells; antibodies are formed based on antigens not present in red blood cells (antibodies formed after antigens)

Question 13

Pedigrees

Answer 13

A chart that traces the inheritance of a certain trait among members of a family

Question 14

Uses of Pedigrees

Answer 14

• Used by geneticists in identifying the way a trait is transmitted
• Useful in counselling parents on the cause of a disease
• Useful in predicting probability of having an affected
  child in subsequent pregnancies

Question 15

Types of Pedigrees

Answer 15

Autosomal Dominant, Autosomal Recessive, X-Linked Dominant, X-Linked Recessive

Question 16

Autosomal Dominant

Answer 16

Usually doesn’t skip generations, equal distribution among sexes

Question 17

Autosomal Recessive

Answer 17

Skips generations, equal distribution among sexes

Question 18

Sex Linked Recessive

Answer 18

Predominantly males affected, father to daughter (daughter is carrier), no father to son transmission, 1/2 daughter’s sons will show trait, trait skips generations

Question 19

Sex Linkage

Answer 19

The passing of traits found on the X chromosome; Y chromosome carries almost no info (too small and missing that segment) –> any gene on X chromosome (in males) will be expressed whether it’s dominant or not (there’s nothing to mask it)

Question 20

Mendel’s First Law of Segregation

Answer 20

1. For each trait, an organism carries two alleles, one from each parent
2. Parent organisms donate only one copy of each gene in their gamete (during meiosis, the two copies separate randomly)