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Biochem > Genetics Exam 2 > Flashcards

Genetics Exam 2 Flashcards

1
Q

How do genes far apart segregate?

A

Independently

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2
Q

How do genes that are linked segregate?

A

With a frequency dependent on the distance from each other

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3
Q

A two-strand double crossover between two linked genes produces?

A

Non-recombinant gametes

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4
Q

Three types of crossovers can occur over three linked loci.

A

Single -> A and B: Swap of B and C
Single -> B and C: Swap of C
Double -> Swap of B

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5
Q

Study

A

Slide 19 Lecture 6

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6
Q

Three methods of mapping genes on chromosomes

A

Deletion mapping
Somatic cell hybridization
In situ hybridization

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7
Q

Deletion mapping

A

A part of the chromosome is deleted and a homozygous cross occurs. If the chromosome displays the recessive gene you know the gene of interest is in the deletion region.

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8
Q

Somatic-cell hybridization

A

Somatic cell hybridization is when two organisms cells are fused together and the hybrid cells are analyzed for certain gene products.

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9
Q

In situ hybridization

A

Attaches probes on sequences to be analyzed. For example fluorescence.

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10
Q

Aneuploidy

A

One set of chromosomes could have more than 2. For example 2n + 1 = 7

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11
Q

Polyploidy

A

All sets of chromosomes have more than 2. For example 3n = 9

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12
Q

Duplication

A

Genes are duplicated -> Looping out is a characteristic in heterozygotes
Can cause unbalanced gene dosage which leads to abnormalities.

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13
Q

Deletion

A

Removal of genes -> Looping out is a characteristic in heterozygotes
Pseudodominance can occur because recessive alleles are expressed
Haploinsufficient can occur when the deleted copy results in a low gene dosage that has a small effect on the wild-type phenomenon.

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14
Q

Inversion

A

Inverts the sequence of the gene on a chromosome -> They can interrupt individual genes, destroying expression. Genes moved around may experience different expressions due to positional effects. Heterozygous inversions lead to decreased crossing over in the inverted region. When crossed over it can cause non-viable gametes.

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15
Q

Translocation

A

Swaps gene sequences from chromosomes -> Has the same effects as inversion

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16
Q

Robertson Translocation

A

A translocation that combines two giant chunks of chromosomes. An example is chromosome 2 on a human.

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17
Q

Three types of segregation

A
  1. Alternate -> Viable
  2. Adjacent 1 -> Non-viable
  3. Adjacent 2 -> Non-viable
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18
Q

Fragile sites

A

Chromosomal regions that are susceptible to breakage under certain conditions.

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19
Q

Causes of Aneuploidy

A

-Loss of centromere
-Small chromosomes -> Robertson Translocation
-Non disjunction either in Meiosis I or II
-Non disjunction in Mitosis

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20
Q

Types of Aneuploidy

A

Nullisomy - Loss of both chromosomes of a pair
Monosomy - Loss of one chromosome
Trisomy - Gain of an extra chromosome
Tetrasomy - Gain of two extra homologous chromosomes

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21
Q

Aneuploidy in Humans

A

Usually lethal, but can lead to individuals with down syndrome

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22
Q

Causes of polyploidy

A

-Non disjunction either in Meiosis I or II
-Non disjunction in Mitosis

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23
Q

Who discovered DNA was a polymer of nucleotides

A

Phoebus Aaron Levene

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24
Q

Who discovered nitrogenous bases were associated with DNA

A

Albrecht Kossel

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25
Q

Who disproved tetra-nucleotide theory

A

Erwin Chargaff 1948

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26
Q

Who first demonstrated bacteria transformation?

A

Fred Griffith -> 1928, however could not explain it.

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27
Q

Who discovered how transformation actually works?

A

Avery, Macleod, and McCarty, discovered that DNase was preventing the bacteria from transforming their genetic information.

28
Q

What is T2

A

A bacteriophage

29
Q

Describe the life cycle of a bacteriophage

A
  1. Phage attaches to a cell and injects its chromosome into the host
  2. The host chromosome is broken apart and integrated into the host chromosome
  3. More phages are produced, host cell is lysed and killed.
30
Q

Hershey Chase Experiment 1952?

A

Discovered that DNA is the genetic material in phages.

31
Q

Heinz Fraenkel-Conrat and Singer demonstrated?

A

That RNA carries the genetic material in TMV (Tobacco Mosaic Virus)

32
Q

Who started studying DNA structure via diffraction?

A

William Ashbury 1947

33
Q

Primary DNA structure

A

String of nucleotides joined together by phosphodiester linkages

34
Q

Secondary DNA structure

A

Three dimensional structure that was discovered by Watson and Crick

35
Q

Tertiary Structure

A

The complex packaging of double helix into chromosomes

36
Q

Three different forms of DNA?

A
  1. A form
  2. B form
  3. Z form
37
Q

How is the primary structure in DNA modified?

A

Through methylation

38
Q

How does DNA condense in tertiary form?

A

By supercoiling

39
Q

Differentiate histone, nucleosome, and chromatin

A
  1. Histone is the protein DNA is wrapped around
  2. Nucleosome is made up of eight histones wrapped together via DNA
  3. Chromatin is the description of the “string and beads” that form tertiary structure.
40
Q

What is histone H1?

A

Acts like a clamp to stabilize DNA around the nucleosome core.

41
Q

30-nm Chromatin

A

Adjacent nucleosomes packing together

42
Q

Types of chromatin

A

Euchromatin -> Less condensed, found on chromosomes, contains most genes, often transcribed.
Heterochromatin -> More condensed, found at centromeres, and telomeres, mostly made of repeated sequences, contains few genes, crossing over is uncommon.

43
Q

Chromosomal puff

A

Indicator of where transcription is actively happening

44
Q

Histone tails and their involvement in transcription

A

When they are positively charged they are tightly bound to the DNA inhibiting transcription factors. Acetylation weakens the interaction causing the DNA to be more accessible.

45
Q

Centromeres

A

Constricted region to which spindle fibers attach during mitosis and meiosis.

46
Q

Telomeres

A

Sequences at the end of chromosomes, highly repeated sequences that interact with proteins.

47
Q

What are required to make Artificial Chromosomes in eukaryotes

A
  1. Telomeric sequences specific to the organism
  2. Centromeric sequences specific to the organism
  3. One or more origins of replication
48
Q

Transposable elements

A
  1. Ubiquitous among forms of life
  2. Comprise of a high percentage of the genome
49
Q

Two major classes of transposons

A

-Dna only
-Retrotransposons (uses RNA intermediate)

50
Q

What ways can transposons drive chromosomal rearrangement?

A

Deletion
Duplication
Inversion

51
Q

Transposable element can cause flanking direct repeats?

A

True

52
Q

Transformation

A

Uptake of DNA from the environment

53
Q

Transduction

A

Phage mediated transfer of DNA

54
Q

Conjugation

A

Transfer via cell to cell contact

55
Q

The F factor

A

Integrated in a bacterial chromosome in an HFr cell

56
Q

R plasmid

A

Conjugative plasmids that carry antibiotic resistance genes

57
Q

Bacteriophages can have two alternative life cylces

A

Lytic
Lysogenic

58
Q

Primary Down Syndrome

A

Three copies of chromosome 21

59
Q

Familial Down Syndrome

A

Translocated chromosome from 21 to 15

60
Q

Specialized transduction

A

Is specific to a certain sequence of the chromosome

61
Q

Types of Inversion

A

Paracentric -> Specific to a certain spot
Pericentric -> Include the centromere

62
Q

F+

A

Present as separate circular DNA

63
Q

F-

A

Absent

64
Q

Hfr

A

Present, integrated into the bacterial chromosome

65
Q

F’

A

Present as a separate circular DNA, carrying some bacterial genes

Biochem (8 decks)

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