Question | Answer |
What are sex-linked genes? | Genes that live on only 1 sex chromosome. The X chromosome carries > 1000 genes; the Y chromosome only 78 genes. |
in multiple allelism, there are multiple genes for one trait. How many alleles are involved in the genes that determine human blood type (A, B, AB, and O)? | Three alleles determine blood type: A, B, O |
explain what Polygenic Inheritance is. | Some characteristics show a range of continuous phenotypes instead of discrete, defined phenotypes (ex: height, skin color, and body build, and grain color in wheat). |
describe what is happening with gene/s involved in Polygenic Inheritance | Phenotypes produced by polygenic inheritance are governed by the interaction of more than two genes at multiple loci
Human skin color is controlled by at least 3 genes, each with pairs of incompletely dominant alleles |
define Pleiotropy. | p. 283 some alleles of a characteristic may create multiple phenotypic effects. Ex: Marfan syndrome, (aka FBN1).
(compare Mendel’s rules that specify only one phenotype possible for any allele)truth is that |
give an example of Pleiotropy in humans. | Example: The SRY gene in male humans'
SRY gene stimulates development of gonads into testes, which in turn stimulate development of the prostate, seminal vesicles, penis, and scrotum |
define Non-Disjunction. | Incorrect separation of chromosomes or chromatids in meiosis |
in Mendel's cross-breeding experiment between a "true breeding" (aka pure breeding) purple flower and a true breeding white flower, what resulted in the F1 and F2 generations? | F1 generation: all purple flowers
F2 generation: 3/4 purple, 1/4 white flowers |
Mendel's reciprocal cross experiments repeated cross breeding. 1st: the trait came from the mother 2nd: trait came from the father. What was the result and what did this prove? | F1 and F2 were identical regardless of whether the traits came from the mother or father, proving that it didn't matter which parent the gene came from. |
Mendel's "genetic model" was later proven by Sutton and Bovieri in which theory? | the Chromosome Theory of Inheritance (13.3, 13.4) |
Demonstrate Independent Assortment by drawing a Punnett square. Both parents have genotype RrYy. Don't fill in squares, just rows and columns to represent the 4 possible gametes genotypes each parent can produce. | p. 273 Independent Assortment:
male parent: genotype RrYy gametes:(RY,Ry,rY,ry)
female parent: genotype RrYy gametes:(RY,Ry,rY,ry)
compare Dependent Assortment:
male parent: genotype: RrYy gametes:(RY,ry)
female parent: genotype: RrYy gametes:(RY,r |
The punnett square for Parents RRYY x rryy results in a F2 Phenotype ratio of 9:3:3:1. Write these in fractions. | p. 273 9:3:3:1
9/16 (R-Y-) (R is dominant, Y is dominant)
3/16 (R-yy) (R is dominant, y is recessive)
3/16 (rrY-) (r is recessive, y is recessive)
1/16 (rryy) (both are recessive) |
In a punnett square for Parents RRYYZZ x rryyzz, how often will the rryyzz genotype show in the F2 generation? | This is like the example on p. 273 but with the additional trait Z. Instead of 4 raised to the 2 (for 2 traits), we raise 4 to the 3 (for 3 traits) and get 64. Thus the all-recessive genotype shows up 1/64 times in F2. |
define locus and loci. | p. 275 A locus (plural: loci) is a gene's physical location on the chromosome. |
Law of Segregation, or Principle of Segregation refers to what stage of meiosis and why? | p. 275 the law refers to the separation of alleles in meiosis. Homologs separate in anaphase of Meiosis I, therefore their alleles separate. They are rejoined at fertilization. |
what is the difference between dominance and incomplete dominance? | p. 283 incomplete dominance: neither allele dominates and there is an intermediate phenotype.
codominance: heterozygotes have the phenotype associated with both alleles present. ex: human RBCs can have membrane glycoproteins have both M and N phenotype. |
what is a qualitative trait? | p. 284-5: A qualitative trait is one that differs by degree (height in humans, kernel color in wheat). |
how is polygenic inheritance linked to qualitative traits? | p286: in polygenic inheritance, each gene adds a small amount to the phenotype. Ex: the number of red pigment alleles A, B, and C in the genotype determine the degree of redness in the wheat kernal. |
is "yellow and wrinkled" an example of a phenotype or a genotype? | a phenotype. Phenotypes describe observable traits. |
Define genetics. | the branch of biology that focuses on the inheritance of traits. |
define a gene | the hereditary determinant for a trait |
Who is Mendel? | an Austrian monk who is considered the father of genetics & the first person who brought math into biology. Mendel’s secret to success: good notes, characteristics chosen, mathematics |
give an example of self-fertilization (aka "selfing"). | the pollen from a garden pea plant's flower falls on the female reproductive organs of that same flower. |
Cross Fertilization ("cross pollination") | this is how Mendel controlled matings to see how traits passed on: he transferred pollen from one flower to the female reproductive organs of another flower. |
define allele | different versions of the same gene |
An individual's collection of alleles is called its ____ | genotype |
An individual's collection of observable traits is called its ____ | phenotype |
What makes an allele recessive or dominant? | a recessive allele disappears in the F1 generation but shows up in the F2 generation at the rate of 1 in 4. |
Does a recessive trait make an individual less fit for survival? | not necessarily. Dominance and recessiveness in traits do not have anything to do with an individual's fitness. Huntington's disease is fatal & rare, from a dominant gene. |
How many alleles do humans have for every gene? | two: one from mom, one from dad. One allele comes from each chromosome in the homologous chromosome pair. |
describe alleles in the Law of Segregation | (p. 275) 2 alleles of a gene separate during meiosis (gametes have 1 allele in 1n or 23 chromosomes), so offspring (sperm + egg = 2n or 46 chromosomes) have 1 allele from mom and 1 allele from dad |
Each selection is an individual's genotype. Which are homozygous for the trait represented by H or h? a) HHKk b) HhKK c) hhkk | a) HHKk and c) hhkk are homozygous |
Each selection is an individual's genotype. Which are homozygous for the trait represented by K or k? a) HHKk b) HhKK c) hhkk | b) HhKK and c) hhkk are homozygous |
Each selection is an individual's genotype. Which are heterozygous for the trait represented by H or h? a) HHKk b) HhKK c) hhkk | b) HhKK is heterozygous |
Each selection is an individual's genotype. Which are heterozygous for the trait represented by K or k? a) HHKk b) HhKK c) hhkk | a) HHKk is heterozygous |
In heterozygous genotype Rr, R represents blue flowers and r represents yellow flowers. What is the dominant phenotype? | the dominant phenotype is blue flowers, represented by R. |
define genotype. | genetic makeup. Mendel worked with phenotype, not genotype, but his work paved the way for its discovery. |
define phenotype. | physical appearance: identifiable traits. |
Mendel's Law of Independent Assortment works in the presence of certain requirements. What are these? | 1) you do not genetic recombination
2) the alleles are not on the same chromosome
3) the alles are on the same chromosome but are more than 50 centi Morgan (cM)apart |
explain what genetic linked (autosomal linked) is. | Different genes locate located on the same chromosome tend to be inherited together: characteristics whose genes tend to assort together are NOT independently assorted, but Linked |
What is a sex linked genes? Do they obey Mendelian laws? | in a sex-linked gene, the allele for the trait is on sex chromosomes. Sex-linked genes do NOT obey Mendelian laws. |
give an example of incomplete dominance. | prediction: SS (straight) X ss (curly) = Ss (straight)
actual: SS (straight) X ss (curly) = Ss (wavy). If SS is straight hair, ss is curly hair, then Ss heterozygous is wavy hair. |
when 2 alleles rather than 1 allele form a new phenotype, what is the word describing their relationship to each other? | they are codominant. |
In a genetic map, what is the unit of distance between two genes? | the unit of distance between two genes is designated by centiMorgans (cM). A cM = the physical distance between 2 alleles that generates 1% recombinant offspring. |
AABb (female) X aabb (male)
which combo would be the fertilized egg?
you need to know the law of segregation and independence
a) AAbb
b) AaBB
c) Aabb
d) none | c) Aabb. One A must come from female (A) and one A must come from male (a). Thus the offspring must have Aa. One B must come from female (B or b) and one B must come from male (b or b), thus offspring has Bb or bb. |
when genes on a chromosome are more distant from each other, are they more or less likely to cross over? | they are more likely to cross over, unless the distance is over 50 cM, in which case independent assortment takes over. |
In the Incomplete Dominance example with lavendar flowers in the text, what colors in what ratios are in F1 and F2 generations? | RR (purple) x rr (white) flower => all F1 have Rr; => F2 is 1:2:1 or RR:Rr:Rr:rr, where Rr is lavendar because neither purple nor white dominate. Note that the 1:2:1 ratio of genotypes matches the 1:2:1 ratio of phenotypes. |
segregation of chromosomes means that | Each gamete formed in an organism will have one copy of each gene. |
two homozygous parents with genotypes RR and rr result in all Rr F1 offspring. Each offspring produces 4 gametes. Where are R and r in the gametes? | Each of the 4 gametes contains R or r, due to independent assortment in meiosis. 2 gametes have R, 2 gametes have r. |
If an individual is heterozygous for hair color (Hh) and eye color (Ee), what genotypes can its gametes have? | Each gamete will contain both genes. Thus the individual can make gametes that contain HE, He, hE, or he. |
If an individual with type O blood mates with an individual with type AB blood, what are the possible blood types of their offspring? | A and B |
define epistasis | When different genes interact with each other in a way that influences the phenotype. |
In Drosophila, the white-eyed gene (w) is on the X chromosome (w+ = red eyes; w = white eyes). The w+ allele is dominant to w. If a w+ homozygous female is crossed with a wY male, what is the phenotypic ratio of the F2 generation? | 2:1:1 (Note that 3:1 is the ratio of red to white). |
If an organism is heterozygous for two traits that are linked, how many genotypes are possible in the gametes produced from a single germ-line cell? (assume no crossing over occurs) | 2, not 4. Remember that linked genes violate the principle of independent assortment. See Figure 13.13. |
If an organism is heterozygous for two traits that are linked, how many genotypes are possible in the gametes produced from a single germ-line cell? (assume 1 crossing over occurs) | 4 See Figure 13.14 |