Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biology > 10.2 > Flashcards

10.2 Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

What is a monohybrid cross

A

examines one trait at a time whilst using punnet squares to check for dominance and sex-linkage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is a dihybrid cross

A

follows the inheritance of two traits, and a dihybrid Punnett square which would give the expected ratio of phenotypes in the offspring If the traits are independently assorted

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What do the outside and adjacent edges of the grid show in dihybrid punnet squares

A

show the possible alleles found in the egg on the outside edge and the possible alleles found in the sperm along the adjacent edge

two different letters are used

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What do the internal boxes show

A

the allele combinations that can be produced by fusion of the gametes

two Paris of alleles, two copies each of two different letters

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What does each square in the punnet grid represent

A

the possible genotype of the diploid offspring

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

if both parents are heterozygous what is the ratio usually in the F2 generation

A

9 : 3 : 3 : 1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is epistasis

A

the effect of one gene depending on the presence of another gene

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What type of genes show independent assortment

A

genes found on different chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are linked genes

A

genes found on the same chromosome, they are physically connected since they occur along he same DNA molecule, but they can often give the same results as unlinked genes in genetic crosses

the closer the loci of two linked genes, the less frequently they are separated by crossing over

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is a linkage group

A

several genes on the same chromosome that do not show independent assortment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How are new allele combinations created

A

by crossing over

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What did Thomas Morgan demonstrate with the help of fruit flies

A

that genes are found on chromosomes and that they do not always follow mendelian ratios

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What types of methods did Morgan use

A

radiation - to cause heritable mutations with visible effects on phenotypes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What was the first clear exception to the Mendelian inheritance

A

found in Drosophila and was the inheritance of white eyes, fruit flies usually have red eyes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What did Morgan establish

A

sex linked trans and suggested that some traits can be located on the sex chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the most common allele of any trait notated in Morgans method

A

with a +

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What happens when two genes are very close together

A

it becomes very rare that a chiasma will form between them, thus, they are almost always inherited together

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How do you show that genes are linked

A

a special notation is used, a capital letter is used for dominance and two horizontal lines represent the homologue chromosomes with one allele for each gene.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the two distinct possibilities for the genotype of a heterozygous parent (using t and b)

A

TB// tb or Tb// tB

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the easiest way to test for a linkage between two genes

A

to use a test cross where a heterozygous parent is crossed with a homozygous recessive parent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What does it mean when something is a recombinant

A

an organism that contains a different combination of alleles to either of its parents

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What do you use for a test cross

A

homozygous recessive parent

23
Q

What does it mean if non-Mendelian ratios are obtained in a dihybrid cross

A

the genes are likely to be linked

24
Q

what is a non-median ratio

A

an unusual ratio of phenotypes such as

3: 5
5: 3
6: 2
2: 6

25
Q

what does it mean the lower the recombinant frequency…

A

the closer the linked genes are on the chromosome

26
Q

What factors can influence phenotype

A
  • more than one gene may affect a single trait
  • a single gene may affect traits
  • a gene may impact the expression of another gene
  • some alleles are not expressed in all individuals
  • some alleles are expressed with varying intensity
  • some genetically influenced traits also have important environmental influences
27
Q

What is an example of a polygenic trait

A

when more than one gene may affect a single trait

for example, the human eye color is polygenic because it is determined lately by two genes with some additional influence from genes on at least a dozen loci

28
Q

What is an example of a pleiotropic gene

A

when a single gene may affect multiple traits

of example, the CFTR gene codes for a transmembrane protein with effects in multiple organs

when the cystic fibrosis allele is homozygous, the functions of the lungs, intestines and pancreas are all affected

29
Q

How may a gene impact the expression of another gene

A

for example the TYR gene produces a polypeptide that is a necessary first step in creating the melanin that gives skin, hair and eyes their many possible colors. When the TYR gene is not functional, the individual will exhibit albinism (lack of pigment) no matter which alleles are present

30
Q

Example of alleles that ae nto expressed in all individuals

A

BRCA1 alleles have incomplete penetrance because even though they greatly increase the risk of breast cancer, some women with the allele never develop it

31
Q

examples of how some alleles are expressed with varying intensity

A

the polydactyl allele in cats (causes extra toes) has varied expressivity because some cats only gave one or two extra toes while others have four extra toes per paw

32
Q

name an example of genetically influenced traits that have impotent environmental influences

A

MC1R gene cause freckling when the skin is exposed to the sun. The development of freckles has both genetic components and environmental aspects related to the amount and intensity of sunlight the individual experiences.

33
Q

What is discrete variation

A

a trait with phenotypes that can be grouped into distinct categories usually coded by a single gene

34
Q

What is an example of discrete variation in genes

A

ABO blood group

35
Q

What is continuous variation

A

traits that display an unbroken range of phenotypes in the population

36
Q

What did Morgan do in his experiment with fruit flies

A

He breezed a white eyes male mutantt with ed eyed female flies:

  • the 1st generation offspring all had red eyes - consistent with mendelian they concerning dominant and recessive traits
  • the 2nd generation contained a small number (roughly 25% of flies) with white eyes - again consistent with mendelian theory
  • however all the white eyed flies were male - this is inconsistent with mendelian theory and suggested that the two traits are linked
37
Q

What characteristics tend to show continuous variation

A

polygenic chacteristics

38
Q

What do traits with continuous variation show

A

an unbroken range of phenotypes in the population

they are often polygenic traits

39
Q

What is the distribution of when gaphsed of continuous variation

A

normal (bell shaped) distribution

40
Q

What is an example of polygenic inheritance

A

height in humans

41
Q

What type of variation is heigh in humans

A

continuous aviation

42
Q

What is involved usually in the orientation of homologous Pais during meiosis and the pairing of gametes in fertilization

A

a random element

43
Q

What does a chi squared test do

A

it assess the edge of difference between observed results and expected results

44
Q

What would the expected ratio in a monohybrid cross between two pea plants heterozygous for pea colour be

A

3: 1

45
Q

What can the chi-squared tell you about your results?

A

how well the observed results compare with the expected results

46
Q

What is the equation for the chi-squared test

A

(obtained - expected)^2 / expected

47
Q

What was the conclusion of Morgan’s discovery about the inheritance of eye colour and shape in Drosophila?

A

the two genes do not ascot independently

they are linked

48
Q

How would you explain a test cross involving dihybrid flies in which parental-type offspring and small numbers of new combinations of parental phenotypes are produced?

A

The two genes are linked on the same chromosome and crossing over has occurred.

49
Q

If three genes control one characteristic, what is the number of possible genotypes produced?

A

27

3^3 = 27

50
Q

Not rejecting the null hypothesis in a chi-squared test calculated in a dihybrid cross indicates that:

A

the predicted ratio of the phenotypes follows the mendelian law

51
Q

In a chi-squared test, the null hypothesis is that two genes are unlinked. The value produced by the chi-squared test was much higher than the critical chi-squared value. What does this indicate?

A

the genes are likely to be linked

52
Q

A heterozygous dihybrid cross resulted in three possible genotypes. What can be concluded?

A

The genes are linked but crossing over did not take place.

Since there are only three resulting genotypes, this means that recombinants are not included. This indicates that the genes are found on the same chromosome (linked) but crossing over did not take place. That is why recombinants were ignored. If recombinants are to be included, the number of outcomes produced should be 16 (4 x 4), with 9 possible genotypes.

53
Q

How would you explain a test cross involving dihybrid flies in which parental-type offspring and small numbers of new combinations of parental phenotypes are produced?

A

The two genes are linked on the same chromosome and crossing over has occurred.

Biology (51 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions