chapter 14 parts 3 & 4

Question 1

What is co-dominance?

- given an describe an example as well.

Answer 1

occurs when two alleles for a gene, neither of which is truly dominant or recessive for a gene.

• so heterozygotes that express both alleles simultaneously.
• like in the A B O blood typing system.
• in the case of red blood cells there is a particular integral membrane protein that is glycosylated (in the golgi).
• but the factors that determine how it is glycosylated depends on what allele or alleles of a gene called the “I” an individual has.
• the A and B allele of I aren’t dominant and recessive to each other .
• But if the A or B allele belongs to i, then the i is recessive.
• I/A,I/A = type A blood: homozygous A individuals, make version of the polysaccharide on that protein, that has a particular monosaccharide on the end of the chain that corresponding to the A allele.
• IA/IB = type AB blood: Half of the membrane bound proteins contain the polysaccharide and end chain monosaccharide to be type A and contain the end chain monosaccharide to be type B.
• IB/IB = type B blood: Homozygous B individuals make a slightly different version of the polysaccaride chain attached to red blood cells, with a monosaccharide on the end of the chain corresponding to the B allele
• IAi = type A blood: half their proteins make the type O polysaccharide chain, and the other half makes the type A polysaccharide chain.
• IBi = type B blood: half their proteins make the type O polysaccharide chain, and the other half makes the type B polysaccharide chain
• ii = type O blood: there version of the polysaccharide doesn’t contain a monosaccharide at the end.

Question 2

What is incomplete (partial) dominance?

give an example

Answer 2

• heterozygous individuals express a phenotype that is in-between or intermediate to the phenotypes of the dominant and recessive alleles.
• ## blending of two alleles.
• example in flowers:
• Begin with homozygous dominant and recessive:
  RR & rr.
• dominant = red flowers and recessive = white flowers.
• if you cross them them you get 50% heterozygous individuals that are PINK.

Question 3

What is polygenic inheritance?

give an example.

Answer 3

• ## a trait is not encoded by a single gene but instead is encoded by many genes.
• Human height:
• if you measure thousands of individuals and their heights in cm, then plot them on graph.
• ## you get a nice bell curve, centered around a particular mean.-ANY TIME YOU MEASURE A CERTAIN TRAIT OF A POPULATION AND THE RESULTS COME BACK AS A BELL SHAPED CURVE
  than it is a quantitative trait, and is caused by polygenic inheritance.
  -

Question 4

What causes quantitative traits?

Answer 4

polygenic inheritance- like with the height example, more than one gene contributes to overall hieght.

Question 5

Describe the example of quantitate traits with agricultural studies.

Answer 5

• inheritance of kernel color in wheat:
• plants can exhibit a wide variety of kernel colors all the way from white all the way to really dark red.
• one can measure the redness of wheat kernels by measuring it over a number of individuals, if you will, and create a plot of the data you experience.
• You will plot a nice bell shaped curve if you will, thus signifying that it is a result of a quantitative trait.
• the majority of the phenotypes seen can be explained by a three genotypes.
• each gene has two different alleles a dominant and a recessive.
• the differing combinations lead to differences in red pigment.

Question 6

what is a pedigree?

explain how it works.

Answer 6

• it is a visual representation of the pattern of inheritance of some trait across generations with in a family.
• you begin by drawing the relationships within a family
• circle = women & square = men
• a horizontal line = individuals breeding.
• a vertical line = direct descendent
• Watch chapter 14. vid 3, 9:00 minutes in of confused.
• then you go back after looking at records and such to piece it together, and follow the trait you are after.
• ## this is done through shading = following a trait you are interested in

Question 7

What does shading on a pedigree represent?

Answer 7

• following a particular phenotype you are after.

Question 8

What is shown within a good pedigree?

Answer 8

• a good representation of a particular trait is passed through a family, which can tell you whether THE TREAT IS CODED BY AN AUTOSOMAL-non sex chromosome or a ( SEX CHROMOSOME).
• WEATHER THE TRAIT IS ENCODED BY A DOMINANT OR RECESSIVE ALLELE.

Question 9

describe an autosomal recessive pedigree?

- vid 3 of chapter 14: 15:30

Answer 9

• you will see males and females equally likely to carry the trait of interest.
• the affected offspring will come from parents that didn’t have the trait, because both parents can be heterozygous.
• meaning one their children will likely by homozygous recessive and show the phenotype for the trait, and 50% will be carriers (heterozygous), and 25% will be homozygous dominant, not having or being being able to pass the trait.
• lots of times the traits can skip generations.

Question 10

Describe an autosomal dominant pedigree?

- vid 3 chapter 14: 15:30

Answer 10

• there is pattern seen in autosomal inheritance: usually one parent is homozygous recessive and the other is homozygous dominant
• this means that 50% of their offspring will display the phenotype

Question 11

What is more ideal larger or smaller pedigree’s?

Answer 11

• larger, more instances to look at.

- small pedigrees can lead to sample size errors.

Question 12

Describe the pedigree of an x linked recessive trait?

Answer 12

• ## The key in distinguishing if it is an x linked trait is determining if there is some unusual pattern of inheritance related to the sex of the individual.
• ## ex: the male has the trait, therefore is homozygous recessive, and some of his grandsons have the trait but non of his grandbitches.

Question 13

Describe the pedigree of an x linked dominant trait?

Answer 13

• The key in distinguishing if it is an x linked trait is determining if there is some unusual pattern of inheritance.
• at first glance looks very similar to an autosomal pedigree, but in an X-linked dominant pedigree..
• if the father has the trait then all his daughters will have the trait, but none of his sons.
• bc the father doesn’t pass an X chromosome on to his sons, but does pass his only X chromosomes on to his daughters .

Question 14

If a trait skips generations this indicates that it is likely..?

Answer 14

a homozygous recessive trait.

Question 15

if a trait is only seen in greater frequencies of men what is it likely a sign of?

Answer 15

classic sign it is an x linked trait.

Question 16

Describe the “and” rule?

Answer 16

• the probability of two independent events occurring at the same time is the product of their individual probabilities.
• if variables are A and B , the if probability = (p), then
  pA x pB = p of two independent events occurring simultaneously.
  —————————————————————————-
• what is the probability of you rolling a six with both di at the same time?
• 1/6 x 1/6 = 1/36.

Question 17

What is the “or” rule?

Answer 17

• the probability of either of two independent events occurring is the sum of their respective probabilities.
• What is the probability of rolling a 5 or a 6?
• 1/6 + 1/5 = 1/3

Question 18

This is an example of a combination of the “and” rule as well the “or” rule.
“ what is the probability of rolling an 11 with two dice?”

Answer 18

• you can get an 11 by rolling a 5 then a six, or a 6 then a five.
• so you treat each pathway as separate by calculating the “and” rule probability of each:
  1/6 X 1/6 = 1/36 & 1/6 X 1/6 = 1/36
  3.) then you take these respective products and apple The “Or” rule of probability.
• 1/36 + 1/36 = 1/18

Question 19

What is the probability of drawing the two of diamonds from a standard deck of cards?

Answer 19

• 4/52 cards are two’s.
• 13/52 cards diamonds.
  (4/52) X (13/52) = 52/2704 = 1/52

Question 20

What is the probability of drawing a face card from the deck: Jack, King , Queen?

Answer 20

• (4/52)- Jack
• (4/52) - King
• (4/52) - Queen
  overall: (4/52) + (4/52) + (4/52) = 12/52 = 3/13

Question 21

Consider the monohybrid cross Aa x Ax, what is the probability that the first offspring will have the recessive phenotype?

Answer 21

• Make a grid: 25%
• the child must get the little a from each parent:
  (1/2) per parent.
• (1/2) X (1/2) = 25%

Question 22

The f gene affects ear size in bunnies. The dominant F allele (floppy ears) & the recessive allele f (straight ears). The B gene affects hair length. The B allele (short hair) is dominant to the b allele (long hair). What is the probability of two double heterozygous parents having a floppy-eared bunny with long hair? Assume genes are not linked.

Answer 22

1.) figure out possible genotypes: FFbb or Ffbb
2.) calculate the probability for each possible genotype.
3.) (1/2) of getting F from dad & (1/2) of getting F from mom.
- (1/2) of getting b from dad & (1/2) of getting b from mom. FFbb = 1/16 = (1/2) x (1/2)
——————————————————————————
4.) via the rule of the monohybrid cross: out comes are 50% heterozygous and 25% homozygous dominant/recessive.
- so if you apple this to the F, then we have a 50% of getting heterozygous F’s.
- and 25% chance of getting homozygous recessive b’s.
- Ffbb = 1/8 = (1/2) x (1/4)
——————————————————————————-
- now we add our probabilities for each respective genotype:
(1/8) x (1/16) = (3/16) chance of floppy-eared and long hair.