Chapter 12.3 - Mendel

Question 1

Cystic Fibrosis Mutation Pedigree

Answer 1

SEE NOTES

Question 2

Gregor Mendel’s 4 Major Contributions

Answer 2

1. Segregation of traits in the gametes
2. Alleles
3. Dominance
4. Alleles for different traits sort into gametes independently

*carefully contained crosses of pea plants with different characters. Pea plants were perfect organisms in this case because all offspring are carefully contained.

Question 3

Character

Answer 3

A heritable feature that varies among individuals

Question 4

Trait

Answer 4

A variant of a character

Question 5

Phenotype

Answer 5

The physical appearance of a particular character

Question 6

Inheritance see graph right under this

Answer 6

How a trait behaves when it’s passed from one generation to the next

Question 7

Self-Fertilization

Answer 7

Offspring will always be the same. The same phenotypein the next generation.

Question 8

Alleles

Answer 8

Alternative alleles (versions of genes) account for variation in inherited characters. DIAGRAM

Alleles encode an enzyme that code for synthesis of a separate pigment.

Question 9

Locus

Answer 9

A defined region of a chromosome where a given gene is located. Alleles are the same genes on the same locus

Question 10

Exon

Answer 10

Encodes portion of the protein

Question 11

Intron

Answer 11

Spliced out of the mRNA

Question 12

Dominance

Answer 12

• if two alleles at a locus differ, the dominant allele determines the phenotype
• dominant alleles are a capital letter and recessive are lowercase

Question 13

Genotype

Answer 13

The specific genetic makeup of an individual usually referring to a particular gene

Question 14

Homozygous

Answer 14

Same two alleles at a locus

Question 15

Heterozygous

Answer 15

Different alleles at a locus

Question 16

The Law of Segregation

Answer 16

• Parental traits (alleles) randomly segregate to the gametes
• Mendel uses a monohybrid (heterozygous for one character) cross to conclude that alleles segregate independently (in gametes)
• Meiosis is the mechanism for segregating alleles
• genotype ratio vs. phenotype ratio*

Question 17

Incomplete Dominance

Answer 17

• Heterozygotes have an intermediate phenotype resulting from not having enough of one enzyme that synthesizes a particular trait ex: pigment via pink flower
• EXAM Q: Phenotypic and Genotype ratios are the same in this case

Question 18

Dihybrid Cross DIAGRAMS

Answer 18

• Mendel also used plants with variations in TWO different characters. In his example, the two characters were seed shape and seed colour
• In the F1 Generation is only the dominant phenotype
• The F2 Generation had a ratio of 9 round yellow: 3 green round: 3 yellow wrinkled: 1 green wrinkled

Question 19

The Law of Independent Assortment

Answer 19

• Genes conferring different characters (ex: seed colour, seed shape) sort independently from one another during gamete formation
• Mendel used a dihybrid to show independent assortment
• Meiosis is the mechanism for independent assortment: alignment of tetrads at metaphase plate

Question 20

Punnet Squares - 4 vs. 16

NEXT DIAGRAM

Answer 20

4: Dependent Ratio of 3:1. Colour and shape are linked
16: Independent Ratio of 9:3:3:1 (dihybrid ratio) colour and shape are independent

Question 21

X-Linked Genes in Humans

Answer 21

• colour blindness
• haemophilia
• Duchenne muscular dystrophy

*about 1100 genes on x chromosome (x-linked) and 75 on Y chromosome diagrams

Question 22

Probability Rules

Answer 22

Multiplication Rule and Addition Rule

Question 23

Multiplication Rule

Answer 23

“What is the probability of getting a white flower in a Pp x Pp monohybrid cross?”

> Probability of 2 independent events occurring together is the product of their individual probability

Question 24

Addition Rule

Answer 24

“What is the probability of getting a purple flower in a Pp x Pp monohybrid cross?”

> The probability that any one of two mutually exclusive events occurring is the sum of their individual probabilities