Brainscape's Knowledge GenomeTM

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


See full index

BIOL 207 Lecture (Genetics: A conceptual Approach 6th/7th Ed) > Lecture 6 > Flashcards

Lecture 6 Flashcards

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

What is the wild type allele?

A

The most commonly found allele in a population

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

If identical alleles are present on both homologous chromosomes, the organism/cell is said to be ______ for that allele

A

Homozygous

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

If one allele is wild type and the other allele is not (I.e mutant allele) the organism/cell is said to be _______ for that allele

A

Heterozygous

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

The known mutant alleles for a given gene plus its wild type allele are referred to as an ________ or _________

A

The known mutant alleles for a given gene plus its wild type allele are referred to as an allelic series or Multiple alleles

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

Define homozygotes

A

A cell/organism with identical alleles of a gene of interest

-Two copies of the same allele

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

Define Heterozygotes

A

A cell/organism with one wild type copy and one mutant allele of a gene of interest

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

If an individual has two mutant alleles that are different from each other, what is this referred to as?

A
  • Hereroallelic - general term

or

-Transheterozygous (drosophila community)

or

-Compound heterozygotes (mice community)

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

Define Hemizygous

A

A situation where a cell/organism has only one copy of a gene/locus/chromosomal region

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

What are two examples of when a hemizygote might be observed?

A

Example 1: deletion - corresponding gene/locus/region is deleted on the homologous chromosome

Example 2: the gene/locus/region occurs naturally in one copy (true for most genes on X or Y chromosomes in an XY individual)

i.e. males are hemizygous for most genes found on sex chromosomes given that they have one X and one Y

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

Complex traits are typically _______ (involving multiple genes)

A

Complex traits are typically Polygenic (involving multiple genes)

-likely derived from multiple genes = exibit large variety of phenotypes

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

Simple traits may be linked to a single gene with multiple alleles. Single gene traits are called ______

A

Monogenic

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

What is complete dominance

A

Type of dominance in which the same phenotype is expressed in homozygotes (AA) and in heterozygotes (Aa); only the dominant allele is expressed in a heterozygote

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

What is haplosufficiency?

A

Simply that one functional copy is sufficient for a wild type phenotype

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

What is incomplete dominance?

A

Type of dominance in which the phenotype of the heterozygote falls in between the phenotypes of the two homozygotes = blending (i.e both alleles contribute to phenotype

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

Define codominance

A

Type of allelic interaction in which the heterozygote simultaneously expresses the phenotypes of both homozygotes

Eg Sickle Cell Anemia: point mutation in haemoglobin

Eg2: Blood type of AO X BO:

Offspring: AO | AB | BO | OO (AB is codominance)

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

Define Haploinsufficiency

A

One functional copy is NOT sufficient for a wild type phenotype

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

Give an example of a heterozygous advantage

A

Hb^S allele: identical to Hb^S except for a missense mutation that provides some protection against malaria

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

What three mechanisms explain how a mutated allele can be dominant:

A
  1. Haploinsufficiency: one wt copy is not sufficient to produce a wt phenotype
  2. Dominant Negative Effect
  3. Gain of Function Effect
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is The dominant-negative effect

A

the gene product from the mutant allele interferes with the gene product from the WT allele (muller’s morph: “antimorph”), thus blocking the wildtype function

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

What is the Gain of Function effect?

A

the mutant allele acquires a new property not present in the WT allele and this new property causes a phenotype (mullers morph - “hypermorph” and “neomorph”

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

Who came up with five classes of mutant alleles?

A

H.J. Muller

Muller’s Morphs

22
Q

Muller’s name for a morph that results in a complete loss of function:

A

“Amorph”

(Modern day called “Null mutation”)

23
Q

What causes an amorph (null mutation)?

Provide three examples

A

Any mutation abrogating the function of a gene:

  1. complete deletion of entire gene
  2. missense point mutation that abolishes all functions of the protein
  3. A nonsense point mutation yielding a truncated, non-functional protein
24
Q

What is Hypomorph?

A

Muller’s term for an allele with partial loss of function.

The allele is still partially functional but not at the level of the wild type gene

25
Q

Two examples that could cause a hypomorph:

A
  1. Mutation in the regulatory element may cause reduced expression of a gene
  2. Point mutation may reduce the activity of the gene product
26
Q

What is porphyrias?

A
  • Group of diseases affecting heme production (there are 8 genes that make heme)
  • the heme biosynthetic pathways are amorphic or hypomorphic
  • Having no heme at all is lethal = at least one allele must have some activity
  • “vampire disease” - injection of blood (heme) or glucose can reduce symptoms and highly sensitive to sunlight
27
Q

What is a hypermorph?

A

Muller’s term for a gene that is active at a level higher than the wild type gene (more protein = more activity)

28
Q

What is an example of how a hypermorph is caused?

A
  • A mutation in a regulatory element (usually non-coding DNA) may increase the expression of a gene resulting in more protein (or RNA)

or

  • A mutation in the coding region may cause the protein to be hyperactive while the protein levels are comparable to the WT allele
29
Q

What kind of change is seen in a hypermorph (qualitative or quantitative)?

A

Quantitative: no new property gained just a higher amount of activity

30
Q

Hypermorph vs Neomorph?

A

Hypermorph: must have increased activity in an area where there was already activity

Neomorph: New activity in a new location (where no previous activity by the gene in question)

31
Q

Myostatin was provided as an example of one of muller’s morphs. What is myostatin and which morph (consider context) is it an example of?

Hint:

Respect to the gene?

Respect to muscle growth?

A

Myostatin is a repressor of muscle growth = mutation means excessive muscle growth

Stop codon truncates myostatin activity

Respect to the gene this is an amorph = stops activity of myostatin

Respect to muscle growth this is a hypermorph

32
Q

What is a neomorph?

A

Muller’s term for a mutation that creates “something new” (gain of function - qualitative)

Allele is active but has acquired a function that the WT gene does not have

33
Q

Provide three examples of how a neomorph might arise

A
  1. A mutation affecting the active centre of an enzyme may alter its substrate specificity
  2. More commonly, a mutation int he regulatory region activates the gene in the wrong tissues or the wrong times (eg Burkitt lymphoma)
  3. Translocations with breakpoints in genes may create new hybrid genes
34
Q

What is Burkitt lymphoma?

A

translocation of an oncogene next to a novel regulatory element

  • MYC gene is under control of REGig regulatory region = activity in an area there shouldn’t be = rapid proliferation = cancer
35
Q

What is an Antimorph?

A

Muller’s term for a “dominant negative”

-Allele is not only active but can override the function of the wildtype allele in a heterozygous setting (different from normal dominance because it isn’t the wild type function of the gene that is causing the dominance)_

36
Q

What are muller’s five morphs

A
  1. Amorph
  2. Hypomorph
  3. Hypermorph
  4. Neomorph
  5. Antimorph
37
Q

What are complementation tests?

A

A tool to categorize mutants

ie allows identification of mutation in different genes

38
Q

Mutations that complement are mutant in different _____ ______ and are called ____ _____ mutations

A

Mutations that complement​ are mutant in different gene loci and are called Non-allelic mutations

39
Q

Mutations that fail to complement (non-complementing) are mutant in the ______ and are called _____ mutations

A

Mutations that fail to complement (non-complementing) are mutant in the same gene and are called allelic mutations

40
Q

Complementation tests are crucial for:

A

The identification of new mutants

41
Q

How do you make a random mutation for genetic screen

A

Classic approach:

  • feed a chemical that induces mutation (mutagen)
  • EMS is a commonly used mutagen - ethylmethane sulfate (G-A transitions and T-C transitions)
42
Q

What are the target nucleotides for EMS (mutagen)

A

G and T

43
Q

How does EMS induce mutations

A
  • EMS is an alkylating agent - adds ethyl group to normal nucleotides (via oxygen on nucleotide)
  • Results in mispairing after replication - Point Mutation
44
Q

How is a genetic screen done?

A
  • mutagenize animals to isolate new mutants
  • Typically thousands of progeny are examined
45
Q

What is the most famous genetic screen? What was the outcome?

A
  • Heidelberg Screen
  • Isolated 600 mutants representing 120 genes
  • Revolutionized our understanding of developmental processes
  • (many of) The discovered genes are conserved between flies and humans (ie homologous)
46
Q

After feeding EMS you have 20 different stocks. What are the two extreme possibilities?

A

Extreme 1: 20 mutations in 20 different genes

Extreme 2: 20 mutations in the same gene

47
Q

What is the overall purpose of a complementation test?

A

Determine whether two mutations represent alleles of the same gene

48
Q

Fail to complement: you can conclude that two mutations have hit ______

A

Fail to complement: you can conclude that two mutations have hit the same gene

49
Q

What is true breeding?

A

Homozygous for a particular gene

50
Q

Consider the case where you have isolated 4 true-breeding lines that have white petals. All you know is the phenotype (white) and that they are true-breeding. How would you determine if they complement (ie if they are on different genes)

  • Purple: AABB or AaBb or AABb or AaBB
  • White: aaBb or aaBB or AAbb or Aabb or aabb
    • ​bold = true-breeding
A

Cross the two genes = if they complement, they will produce purple offspring

BIOL 207 Lecture (Genetics: A conceptual Approach 6th/7th Ed) (9 decks)

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