7B Midterm

VNTR

(variable number of tandem repeats) tandem (next to each other) repeats of a short DNA sequence (9 to 80 base pairs) with varying numbers of repeats among individuals

How to tell if a trait is sex-linked 1. Sex linked recessive 2. Sex linked dominant

1. Sex linked recessive: - More males are affected. - If a female has the trait, her father must also express it; her mother may or may not - If a female has the trait, and her father does not, the trait is autosomal recessive - If a recessive sex-linked trait is expressed by the male, none of his sons will inherit it from him but it may appear in the sons of his daughters (his daughters will be carriers) - If mother shows the phenotype, every son would have to show the trait Sex linked dominant - Dad has it, daughters must have too

Prophase I

1. Synapsis- pairing of homologous chromosomes and forms a tetrad: consists of 4 chromatids in a homologous pair 2. Crossing-over: homologous cross-over and exchange segments. The exchange includes the breaking and rejoining of two different chromatids. 3. Chiasmata- points of chromosome exchange (when they cross over)

Two parents have a third and fourth child. What is the probability that one child is a girl and the other is a boy?

1/2 This is because the two events are independent from each other. If you wanted the third child to be male and the fourth child to be female, you would do 1/2 x 1/2

Anaphase I

CHROMOSOMES segregate - one chromosome of each homologous pair moves to opposite poles of the cell - homologous chromosomes segregate

In humans, how many pairs of homologous chromosomes are present in a single cell at the end of meiosis II? A. 0 B. 11 or 12 C.23 D.46 E. 92

There are no more pairs so 0

An individual who is heterozygous for two linked genes (with alleles A, a and B, b) is crossed with an AB/ab individual, and among the progeny are:14 AB/ab, 36 Ab/ab, 34 aB/ab, 16 ab/ab What is the frequency of recombination? 0.40 0.35 0.30 0.70 0.60

0.3

Given: C: pigment c: no pigment I: inhibitor i: no inhibitor I is epistatic to C You cross CcIi x CcIi What ratio of white to brown (pigmented) chickens would u expect to observe in the F2 generation?

13:3

Consider a gene with four alleles: A1, A2, A3, and A4. In the cross A1A2 × A3A3, how many offspring genotypes are possible? a. 4 b.2 c.6 d.5 e.3

2

How many chromosomes in the beginning of mitosis

23

Multiple alleles

3 or more alternate alleles for 1 trait Only 2 are present at a given time in an individual organism Ex: Human blood groups

How many chromosomes in the beginning of meiosis

46 chromosomes

In genetics, the dash symbol (-) is a "wild card" that stands for either the dominant allele or the recessive allele; for example, A- means the individual has either the genotype AA or Aa. Two genes that undergo independent assortment affect the shape of the seed capsule in the broadleaf weed known as shepherd's purse. Each gene has two alleles, one of which is dominant for the shape of the seed capsule. Genotypes of the form A- B-, A- bb, and aa B- have triangular seed capsules, whereas the seed capsules of aa bb genotypes are ovoid. What ratio of triangular : ovoid is expected from the cross Aa Bb x Aa Bb? a. 15:1 b. 12:4 c. 13:3 d. 10:6 e. 9:7

A

With independent assortment, the ratio of genotypes in the F2 generation of a cross between true-breeding strains (AA bb x aa BB) can be described as 1:2:1:2:4:2:1:2:1. To what genotype does the "4" in the ratio refer? a. Aa Bb b.AABb c.AaBB d. None of the options above

A

Hemophilia is a sex-linked recessive trait in humans. If a carrier female (heterozygous for the trait) mated with a non-affected male, what would be the expected outcome(s)? Select all that apply. a. None of the daughters would have hemophilia. b. Half the daughters would have hemophilia. c. Half the sons would have hemophilia. d. None of the offspring would have hemophilia.

A and C

An individual who is heterozygous for two linked genes has the genotype AB/ab, which means that the A and B alleles are in one chromosome and the a and b alleles are in the homologous chromosome. Among the products of meiosis listed, which would be the recombinant types? Select all that apply. a. AB b. aB c. Ab

B and C

If you crossed two heterozygous yellow-seed pea plants (genotypes Aa), the relative frequency of: a. homozygous yellow-seed plants (genotype AA) would be 1/4. b. green-seed plants (genotype aa) would be 1/4. c. the a allele in each parent's gametes would be 1/2. d. the A allele in each parent's gametes would be 1/2. e. All of these choices are correct.

All of these choices are correct

General rule for pedigrees

Any time two parents are phenotypically different from the child, the parents must be heterozygous, and the child will be homozygous recessive.

Red-green color blindness is due to a mutant gene in the X chromosome. An XX female with normal color vision and an XY male with normal color vision have a child with karyotype XXY who is color blind. The likely explanation is that the: a. father had CNV of the color-blind mutation. b. mother was heterozygous for the color-blind mutation. c. None of the other answer options is correct. d. father was heterozygous for the color-blindness mutation. e. mother had CNV of the color-blind mutation.

B The mother's X chromosome with the color-blind allele had a non disjunction in meiosis II so that both chromatids with the color-blind allele ended up in the same gamete that was then fertilized to produce the color-blind son.

A pea plant is heterozygous (Aa) for seed color and heterozygous (Bb) for seed shape. Which statements are correct according to Mendel's principle of independent assortment? Select all that apply. a. A gamete that contains the dominant allele for seed color must also contain the dominant allele for seed shape. b. A gamete that contains the dominant allele for seed color is equally likely to contain the dominant or the recessive allele for seed shape. c. Possible gamete genotypes are AB or ab; each is equally likely to occur. d. A gamete that contains the dominant allele for seed color must also contain the recessive allele for seed shape. e. Each gamete will contain either a seed-color allele or a seed-shape allele, but not both.

B and c

Considering an X-linked dominant trait, if an unaffected woman and an affected man decide to have children, which of the answer choices is possible for their children? A. Their sons are expected to be heterozygous for the gene. B. Their daughters are expected be heterozygous for the gene. C. All of their sons are expected to show the dominant trait. D. All their children, whether male or female, are expected to show the dominant trait. E. Their daughters are not expected to show the dominant trait.

B. All female offspring will inherit an affected X from the father, and an unaffected X from the mother. We know the mother is not a carrier because the trait is dominant.

If a nondisjunction occurred in one cell at meiosis II instead, how many cells will have an incorrect number of chromosomes? A. 0 B. 1 C. 2 D. 3 E. 4

C

Recall that a dihybrid cross gives a phenotypic ratio of 9:3:3:1. What is the probability that two CcFf cats will give brith to a striped kitten A. 3/4 B. 9/16 C. 1/4 D. 3/16 E. 1/16

C

Suppose a child is blood group AB. Which of the following pairs of individuals could represent the parents of this child? A. AB x O B. A x O C. A x AB D. O x O E. More than one of the above

C

X-linked genes show crisscross inheritance because males: a. get their X chromosome from their father. b. get their Y chromosomes from their father and transmit their Y chromosomes to their sons. c. get their X chromosomes from their mother and transmit their X chromosomes to their daughters. d. transmit their X chromosome to their sons.get their Y chromosome from their father. e. transmit their Y chromosome to their sons.

C Males only have one copy of an X chromosome and will show an X-linked recessive trait. When they pass on their X to their daughters they will likely be heterozygous with one wild type of X chromosome, and the trait will be masked in the heterozygous condition

Among the progeny of a heterozygous round (Aa) x homozygous wrinkled (aa) testcross, three seeds are chosen at random. What is the probability that all three seeds are round? a. 3(1/2)^3 b. (1/2)^3 c. 2(1/2)^3 d. 4(1/2)^3

b

A mutation that changes one amino acid into another is called a: A. Silent mutation B. Frameshift mutation C. Point mutation D. Missense mutation E. Nonsense mutation

D

Consider a gene with four alleles: A1, A2, A3, and A4. How many distinct heterozygous genotypes are possible? a. 4 b.2 c.3 d.6 e.5

D

Consider a gene with n alleles A1, A2, ..., An. How many distinct heterozygous genotypes are possible? a. n^2/2 b. n(n + 1)/2 c. n^2 d. n(n- 1)/2 e. n(n-1)

D

Imagine non-disjunction occurs in chromosome 14 in a human during meiosis II. What would be the number of chromosomes in the resultant gametes? A. 23, 23, 23, 23 B. 23, 23, 24, 24 C. 22, 22, 24, 24 D. 23, 23, 22, 24 E. 23, 23, 23, 22

D

In genetics, the dash symbol (-) is a "wild card" that stands for either the dominant allele or the recessive allele; for example, A- means the individual has either the genotype AA or Aa. Two genes that undergo independent assortment affect fruit color in summer squash. Each gene has two alleles, one of which is dominant for fruit color. Genotypes of the form A- B- and A- bb have white fruit, genotypes of the form aa B- have yellow fruit, and genotype aa bb has green fruit. What ratio of white : yellow : green is expected from the cross Aa Bb x Aa Bb? a. 9:6:1 b. 9:3:4 c. 10:3:3 d. 12:3:1

D

Recall that a dihybrid cross gives a phenotypic ratio of 9:3:3:1. What is the probability that two CcFf cats will give birth to a solid kitten with straight ears? C is Solid F is folded A. 3/4 B. 9/16 C. 1/4 D. 3/16 E. 1/16

D

RFLP

Differences in DNA sequence on homologous chromosomes that can result in different patterns of restriction fragment lengths (DNA segments resulting from treatment with restriction enzymes); useful as genetic markers for making linkage maps.

Map units

Distances between genes can be expressed as map units; one map unit represents a recombination frequency of 1%

In a diploid individual, there are two genes called "A" and "B" on one chromosome. One homolog of that chromosome carries A and B alleles of those genes, and the homologous chromosome carries different forms (alleles) of these same genes, a and b. If there is a single crossover between these two genes involving one pair of non-sister chromatids during metaphase I of meiosis, the resulting four gametes would be: a. AB, ab, AB, ab. b. AB, AB, ab, ab. c. Ab, Ab, aB, aB. d. AaBb, AaBb, AaBb, AaBb. e. AB, Ab, aB, ab.

E

Suppose a child is blood group O. Which of the following pairs of individuals could represent the parents of this child? A. ABxO B. AxO C. AxAB D. OxO E. More' than'one' of'the' above

E

The mitochondrial DNA sequences of a large extended family were analyzed and compared to a single male in the family. Which of the relatives' mitochondrial DNA should be a match to this person? a. his paternal grandmother b. his brother's daughter c. his maternal grandfather d. his children e. his sister's son

E Mitochondrial DNA are passed from the mother to offspring. A male in the family will share the same mtDNA as his sister, and the sister would have passed on the same mtDNA to her son.

An individual is heterozygous for two linked genes, but whether its genotype is AB/ab or Ab/aB is not known. The individual is crossed with an ab/ab individual, and among the progeny are: 16 AB/ab; 54 Ab/ab; 46 aB/ab; 24 ab/ab.These results imply that the genotype of the doubly heterozygous parent was AB/ab. a. True b. False

False

The result of sexual reproduction is genetic variability in offspring. The 3 ways in which genetic variability is increased through sexual reproduction are

Fertilization Recombination Independent Assortment

mtDNA

Genetic material found in mitochondria. It is passed down from mothers to both sons and daughters, but sons cannot pass along their mothers' mtDNA to their children. This is because mtDNA is transmitted through the female egg. The mtDNA found in the egg is nonrecombinant, meaning that it does not combine with any other DNA so that it is passed down virtually unchanged through the direct maternal line over the generations.

Diploid organisms

Have evolved to have 2 copies of each gene (one on each homologous chromosome), possibly as a genetic backup. When one gene has been changed or mutated, there is still one functional allele that will produce enough of the gene product to show the normal phenotype.

Heritable vs Sporadic

Hereditary is passed from parents to their children and sporadic cancers arise from gene damage acquired from environmental exposures

Norm of Reaction

How environment affects phenotype across a range of environmental conditions, shows evidence of phenotypic plasticity for a genotype Ex: Hydrangea flower color is determined by soil pH

Dominantly inherited disorders

Huntington's disease Acondroplasia Diseases caused by dominant alleles are not as common in the population as diseases caused by recessive alleles. This is because with recessive diseases, heterozygotes are phenotypically normal, and thus live to a reproductive age and pass on their genes. However, dominant disease alleles are phenotypically expressed in the heterozygote and there for the heterozygotes usually does not live to reproductive age and doesn't pass on the disease allele

How to tell if a trait is autosomal recessive

If 2 parents do not have the trait, and their children show the trait Recessive traits tend to skip generations and don't show up as often

How to tell if a trait is autosomal dominant

If 2 parents have the trait and their child does not have the trait Usually dominant traits are present in all generations

Genetic predisposition

If a person inherits one mutant recessive allele, he or she is said to have a genetic predisposition for acquiring the disorder related to that allele during his or her lifetime

You are tracing the family history of Fluffy. Fluffy is male and has three brothers who are all striped with folded eats. Fluffy's mother is solid with folded ears and his father is solid with straight ears. Fluffy's maternal grandmother is solid with straight ears Fluffy's maternal uncle is solid with folded ears

Look at slides 6-10 on Week 2

Polygenic Inheritance

Mode of inheritance in which the additive effect of 2 or more genes determines a single phenotypic trait Ex:Skin color, height, intelligence, eye color The distribution pattern of this type of inheritance often shows a bell-shaped curve

Boys get their X chromosome from the

Mom

Incomplete Dominance

Neither one of the two alleles is dominant to the other; both are expressed equally as an intermediate phenotype in a heterozygous individual (phenotypes appear to be blended)

If a cell has a diploid number of six (2n=6) before meiosis, how many chromosomes will be in each of the four daughter cells if one pair of chromosomes experiences nondisjunction during meiosis I? How many chromosomes will be in each of the four daughter cells if one pair of chromosomes experiences nondisjunction during meiosis II?

Nondisjunction during meiosis I: 4,4,2,2 Nondisjunction during meiosis II: 4,2,3,3

Epistasis

One gene at a locus will affect a different gene at a different locus Ex: 2 gene loci (that code for 2 enzymes) control 2 different steps in a biochemical pathway that produces a phenotype Locus 1--> BB grey, Bb, bb brown Locus 2--> CC color, Cc, cc albino Anytime cc is present, no pigment is produced and the albino condition results The c locus influences the b locus (the c locus is epistatic to the b locus)

Allele

Particular form of a gene; different alleles have different DNA sequences

Interphase

Prior to meiosis I, the cell will replicate its DNA, and 2 sister chromatids are formed

Telophase I

Reorganization of the nucleus

Gene

Segment of DNA that influences one or more phenotypes

For example, C> ck> cd> ca CC-Black ckck- Sepia cdcd- Cream caca- Albino What's the color of a ckcd guinea pig

Sepia

SNP

Single nucleotide polymorphism, change of base of single DNA nucleotide

Regression Line

Slope= 1.0 if variation is just due to genetic variation Slope=0 if variation is just due to environmental variation

Meiosis

Special nuclear division to form gametes The number of chromosomes is reduced by half (diploid to haploid)

Locus

Stretch of DNA at a particular location on a chromosome

The product rule

The probability of 2 independent events both occurring together is equal to the product of their independent probabilities

Mendel's Principle of Segregation

The two alleles of a gene segregate equally into gametes so that half the gametes get one allele and half get the other allele

Neurospora Spores

Usually, without crossing over, it would be 4 black and 4 white colored spores in a row But if there were crossing over, the black and white spores would be mixed

Nondisjunction

When homologous chromosomes do not separate correctly from one another in anaphase of meiosis I or when chromatids do not separate from one another in anaphase of meiosis II This usually results in the production of nonviable gametes

hierarchy of dominance

When there are multiple alleles for the same trait and can both be present. But there is a hierarchy, and when one is dominant over the other, that will show

If a male has a mutation on his X chromosome and has 2 daughters, will they be carriers of the mutation

Yes

Which of the following observations demonstrates Mendel's principle independent assortment? a. An individual with red hair is no more or less likely to be taller than anyone else b. More men than women are colorblind c. Some traits are more likely to be genetically inherited than others d. A diploid individual passes on only one copy of a gene to their offspring e. None of the above

a

Suppose that in humans the ability to roll the tongue (R) is dominant to being unable to roll it (r). Having freckles (F) is dominant to having no freckles (f). A freckled tongue-roller could have which genotypes?Select all that apply. RRFF RrFf All of these choices are correct. RRff and RrFf only rrFF

a and b

Genetic Marker

a gene or short sequence of DNA used to identify a chromosome or to locate other genes on a genetic map.

Genes vs. Environment

a) Genetically different All corn plants are grown in the same environment, so differences in height are due to genetic differences b) Genetically identical strains of corn When all the corn plants are genetically identical, so differences in height are due to environmental differences

Imagine that a rancher has a herd of cattle with brown hides and short horns. All of his cattle are also relatively short in stature. If all of these were true-breeding traits, what could you say about the progeny of these cattle? a. The progeny of these cattle will have a mix of brown, black, white, and spotted hides. b. The progeny of these cattle will be short in stature and have brown hides and short horns. c. It is impossible to determine which traits will occur among the progeny—they will likely demonstrate different hide colors, horn lengths, and heights. d. The progeny of these cattle will have short horns but a variety of hide colors and heights. e. Since the cattle are true breeding, the progeny of this herd will all be sterile.

b

Given equal probabilities of the birth of a boy or girl, what is the probability that a group of four siblings includes all boys? All girls? All boys or all girls? a. 1/8; 1/16; 3/8 b. 1/16; 1/16; 1/8 c. 1/16; 1/16; 1/64 d. 1/16; 1/8; 3/8

b. In the mating of an XX female and XY male, 1/2 the offspring will be male and 1/2 will be female. The probability of all boys is (1/2)^4, the probability of all girls is the same. The probability of all boys or all girls is the sum of these probabilities: 1/16 + 1/16 = 1/8

A true-breeding black rabbit is crossed with a true-breeding white rabbit to produce an F1 generation of 16 individuals. If the black color trait is dominant, which of the outcomes represents the expected phenotype of an F1 generation cross? a. 5 black rabbits, 4 white rabbits, 7 gray rabbits b. 9 black rabbits, 3 white rabbits, 3 gray rabbits, and 1 spotted rabbit c. 16 black rabbits, 0 white rabbits, 0 gray rabbits d. 0 black rabbits, 16 white rabbits, 0 gray rabbits e. 0 black rabbits, 0 white rabbits, 16 gray rabbits

c

In the F2 generation of a homozygous round (AA) × homozygous wrinkled (aa) cross in peas, two seeds are chosen at random. What is the probability that one is round and the other is wrinkled? a. (3/4) × (1/4) b. (3/4)^2 c. 2 × (3/4) × (1/4) d. (1/4)^2

c

You are given two populations of true-breeding tomato plants with two simple dominant/recessive traits that sort independently. Using the multiplication rule, how many different phenotypic combinations would you expect to see in the F2 generation? In what phenotypic ratio? two; 3:1 three; 9:6:1 four; 9:3:3:1

c

Dihybrid crosses Heterozygous for 2 traits x Heterozygous for 2 traits

crosses that examine the inheritance of two different traits 1/16 AABB 2/16 AABb 2/16 AaBB 4/16 AaBb 1/16 AAbb 1/16 Aabb 1/16 aaBB 2/16 aaBb 1/16 aabb Ratio of phenotypes: 9:3:3:1 9- Dominant both traits 3- Dominant for A trait but recessive for b trait 3- Dominant for B trait but recessive for a trait 1- Recessive for both traits

In genetics, the dash symbol (-) is a "wild card" that stands for either the dominant allele or the recessive allele; for example, A- means the individual has either the genotype AA or Aa. Two genes that undergo independent assortment affect coat color in mice. Each gene has two alleles, one of which is dominant for coat color. Genotypes of the form A- B- have a brownish color called agouti, A- bb are black, and aa B- and aa bb are albino (white). What ratio of agouti : black : white is expected from the cross Aa Bb x Aa Bb? a. 10:3:3 b. 12:3:1 c. 9:6:1 d. 9:3:4

d

Which of the examples would be good examples of genotype-by-environment interactions? Select all that apply. a. two different strains of corn that differ in height due to genotype b. a line of chickens whose eggshells are extra thick regardless of feed type c. two different mutants of mice that share similar fat metabolism abilities d. a line of dairy cows that increases milk yield in relation to feed amount e. a strain of mutant mice that becomes obese regardless of feed amount f. a strain of corn whose yield varies with the amount of nutrients in the soil

d and f

A normal XY male has a son with the karyotype XYY. The likely explanation is: a. dosage compensation. b. translocation. c. copy-number variation. d. first-division nondisjunction. e. second-division nondisjunction.

e Only nondisjunction in the second meiotic division could produce sperm with two Y chromosomes. Nondisjunction in the first meiotic division can only produce XY or 0 sperm.

Metaphase I

homologous pairs line up on the equator - Independent assortment occurs: allows for genetic variation

Non-disjunction in meiosis I

n+1, n+1, n-1, n-1

Non-disjunction in meiosis II

n+1, n-1, n, n

Crossing over

when homologous chromosomes exchange genes during Prophase 1 creating new mixture of parent traits in their offspring Allows for genetic recombination (produces variation in gametes, which results in more variation in offspring)

Environmental factors and genetics

• Non genetic factors like diet, pollution, smoking, and exercise can also have an impact on the development of cancers and other diseases • Environmental factors also impact a number of complex traits