Chapter 13: Mendel and the Gene

Question 1

heredity

Answer 1

transmission of traits from parents to offspring via genetic info

Question 2

allele

Answer 2

a particular version of a gene

Question 3

genotype

Answer 3

all of the alleles of given gene present in an individual…

Question 4

trait

Answer 4

any characteristic of an individual (ie. eye colour, skin tone, etc.)

Question 5

phenotype

Answer 5

physical/physiological traits of an individual which are determined by its GENOTYPE

Question 6

cross fertilization

Answer 6

mating that combines gametes from different individuals

Question 7

hybrid

Answer 7

offspring of parents from 2 different populations

Question 8

dominant allele

Answer 8

an allele that determines the phenotype of a heterozygous individual

Question 9

recessive allele

Answer 9

an alleles only whose phenotype observed in HOMOZYGOUS individuals

Question 10

heterozygote

Answer 10

have 2 different alleles (dominant and recessive) of a gene

Question 11

homozygote

Answer 11

have 2 identical alleles of one gene

Question 12

punnet square

Answer 12

diagram showing the genotype and phenotypes of certain offsprings after certain crosses

Question 13

What were the studied variable traits in garden peas by Mendel? (hint: 7 traits)

Answer 13

seed shape, colour;pod shape and colour; colour of flower, the stem length;flower and pod position

Question 14

What 2 questions did Mendel want to answer regarding heredity?

Answer 14

1) BLENDING INHERITANCE: traits observed in a mom and dad will blend together to form the traits observed in their offspring (ie. black male dog and white femal dog will produce a grey dog)
2) INHERITANCE OF ACQUIRED TRAITS: traits in parents are modified through use and passed on to their offspring in THAT modified form (ie.giraffes acquired longer necks from reaching for tall plants and passed this trait on to their offspring)

Question 15

Is the inheritance of seed shape (or any of the pea traits) affected by whether the genetic determinant is a male or female gamete?

Answer 15

Makes no difference whether genetic determinant for seed shape comes from male or female gametes.

Question 16

Why did round and wrinkled seeded plants exist in a 3:1 ratio (round:wrinkled)?

Answer 16

1) Principle of Segregation

2) Hypothesis of independent assortment

Question 17

Monohybrid Cross

Answer 17

a mating between 2 parents that are both heterozygous at the gene in question

Question 18

Dihybrid cross

Answer 18

a mating between 2 parents that are both heterozygous for two traits

Question 19

Does the principle of segregation hold true if individuals differ in 2 traits?

Answer 19

yes

Question 20

Principle of Segregation

Answer 20

: the 2 alleles of each gene must separate into different gamete cells during meiosis…each gamete contains an allele of the gene

Question 21

Hypothesis of independent assortment

Answer 21

each pair of hereditary elements (alleles of the same gene) behaves independently of other genes during meiosis

Question 22

Chromosome Theory of Inheritance

Answer 22

states that Mendel’s rules can be explained by the independent alignment and separation of homologous chromosome pais at meiosis I

Question 23

wild type (fruit flies experiment)

Answer 23

the MOST common phenotype of a trait…red eyes in fruit flies

Question 24

mutant (fruit flies)

Answer 24

a change in a gene that alters phenotype/genotype…white eyes in fruit flies

Question 25

what did Hunt Morgan find when he mated a female wild type and a male mutant?

Answer 25

all the F1 generation were red-eyed

Question 26

How about a female (white eyed) mutant with male wild type? (reciprocal cross)

Answer 26

the F1 gen. consisted of white eyed males and red-eyed females

Question 27

What did Nettie Stevens noticed about the chromosomes in females and males insects?

Answer 27

females=20 large chromosomes (XX)
males=19 large chromosomes and 1 small one (XY)
X and Y chromosomes differ in shape and size

Question 28

What did Morgan predict?

Answer 28

that the genes for red of white eye colour was linked to the X chromosome and that the Y chromosome did not carry allele for eye colour

Question 29

x-linked inheritance (x-linkage)

Answer 29

gene resides on X chromosome

Question 30

y-linked inheritance (y-linkage)

Answer 30

gene resides on Y chromosome

Question 31

sex-linked inheritance

Answer 31

gene is on either sex chromosome

Question 32

Why was Mendel’s Principle of Independent Assortment re-evaluated?

Answer 32

• genes could not undergo independent assortment if they were located on the same chromosome
• genes are physically linked and are inherited together

Question 33

gene-linked (linkage)

Answer 33

2 or more genes are located on the same chromosome (diff. from sex-linked)

Question 34

Why are there 4 genotypes when a red-eyed, gray-bodied female was mated with a white-eyed, yellow-bodied male?

Answer 34

Crossing over of genes…recombination

Question 35

recombination

Answer 35

results from crossing over of genes between homologous chromosomes leading to new genotypes formed

Question 36

What did Morgan conclude (regarding the violation of independent assortment)?

Answer 36

-that linked genes are inherited together UNLESS crossing over happens between them, resulting in recombination

Question 37

Why didn’t the 2 recombinant genotypes occur as frequent as the other?

Answer 37

distance between the genes is critical for the FREQUENCY of recombination

• is rare if genes are close together on chromosome
• is more frequent if genes are farther apart on chrmosomes

Question 38

the effect a single gene has on an organism phenotype is based on:

Answer 38

1) individual’s physical environment

2) alleled present at other gene loci (specific location of a gene)

Question 39

Examples of when the physical environment impacts phenotype

Answer 39

• mice:their agouti coat colour (need more info)
• human: PKU (phenylketonuria)–sufferer lacks an enzyme that helps convert phenylalanine (AA) to tyrosine (AA) and accumulation of phenylalanine can lead to nervous system damage and mental retardation–if person refrains from eating foods containing phenylalanine, can develop normally.

Question 40

Examples of when the genetic environment impacts phenotype

Answer 40

-if a yellow and brown pepper were mated and produced a red pepper, which produced yellow/brown/red/green peppers

Question 41

What is epistasis?

Answer 41

one gene can impact the action of another gene; can mask or reduce the effect of another gene

Question 42

What are discreet traits?

Answer 42

traits that are qualitatively different (green vs. yellow)

Question 43

What are quantitative traits?

Answer 43

• individuals differ by a degree
• range of values; variation
• highly influenced by environment
• distribution of traits form bell curve

Question 44

Polygenic inheritance

Answer 44

each gene adds a small amount to the value of the phenotype

Question 45

What are the problems with mapping diseased traits in humans?

Answer 45

• don’t have pure lines

- can’t control mating

Question 46

What is a pedigree (family tree)?

Answer 46

a record of genetic relationship among individuals in a family, along with their sex and phenotype with respect to the traits in question

Question 47

What info can be obtained from a pedigree?

Answer 47

• whether trait is governed by a single gene
• whether phenotype is due to a dominant or recessive allele
• whether responsible gene for disease is located on sex chromosome or autosome

Question 48

Who are considered ‘carriers’ of a disease?

Answer 48

heterozygous individuals who carry a recessive allele for an inherited disease but don’t exhibit signs of the disease

Question 49

If 2 carriers mate, then how much of their offspring will have the recessive phenotype (the disease)?

Answer 49

25% or 1/4 of their offspring

-do punnett square for Rr x Rr

Question 50

When would a recessive phenotype show up in offspring?

Answer 50

-when both parents have the recessive allele and pass it on

Question 51

I the phenotype is autosomal recessive, the traits are:

Answer 51

autosomal recessive

Question 52

Autosomal dominant traits

Answer 52

if a trait is autosomal dominant, individuals who are heterozygous (Hh) and homozygous (HH) must have the dominant phenotype

Question 53

Sickle cell disease

Answer 53

autosomal recessive inheritance

Question 54

Huntington’s disease

Answer 54

autosomal dominant inheritance

Question 55

If traits appear approx. equally in males or females, then:

Answer 55

the traits are likely autosomal

Question 56

If males are more likely to have the trait than females, then:

Answer 56

allele is likely recessive and x-linked