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Biosci 202 > Lecture 4, 5, 6, 7 & 8 > Flashcards

Lecture 4, 5, 6, 7 & 8 Flashcards

1
Q

Locus

A

the specific place on a chromosome where a gene is located

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2
Q

each individual has 2 alleles, however…

A

there can be many different alleles in the population (sometimes >100)

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3
Q

Mitosis (x4)

A
  • 1 division
  • 2 identical daughter cells
  • Somatic cell
  • For growth and repair
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4
Q

Meiosis (x3)

A
  • 2 divisions
  • 4 haploid daughter cells
  • for the production of sperm/egg/gametes
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5
Q

heteromorphic chromosomes

A

different looking chromosomes

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6
Q

What did the Datura plants show

A

Are aneuploidy- addition of new chromosomes created different looking plants -> chromosomes = different and carry genes

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7
Q

What did Morgans data show

A

That linked genes in a dihybrid may be present in 2 configurations:

  • Cis configuration
  • Trans configuration
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8
Q

Cis Configuration

A

(adjacent) the 2 dominant alleles are present on the same homolog

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9
Q

Trans Configuration

A

(opposite) the 2 dominant alleles are on different homolog

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10
Q

Result from dihybrid crosses & linkage (ratios)

A
  • 2 equally frequent NON-RECOMBINANT classes totaling GREATER than 50%
  • 2 equally frequent RECOMBINANT classes totalling LESS THAN 50%
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11
Q

What is the relationship between distance and amount of crossing over and recombination

A
  • further apart = more crossing over & higher recombination number
  • closer together = less crossing over, very low recombination number
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12
Q

Morgan suggested that recombination is bought about by…

A

Chiasma formation

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13
Q

When does Chiasma formation occur

A

during zygotene/pachytene of meiotic prophase 1

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14
Q

What is Chiasma

A

Sites of crossing over

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15
Q

Morgan’s Data

A

homozygous recessive X homozygous dominant

=heterozygous

F1: heterozygous X homozygous(tester) = F2 ( P, P, Recombinant, recombinant)

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16
Q

INTERchromosomal recombination

A

the genes are on DIFFERENT chromosomes resulting in EQUAL frequencies of recombinant and partenal classes

p: 1/4
p: 1/4
r: 1/4
r: 1/4
1: 1:1:1 ratio

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17
Q

INTRAchromosomal recombination

A

Mediated by CHIASMA FORMATION where the RECOMBINANT classes are LESS frequent.

p: >1/4
p: >1/4
r: < 1/4
r: <1/4

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18
Q

Bivalents are…

A

paired homologous chromosomes. Formed during recombination
aka Tetrad
contain 4 chromatids or 2 pairs of sister chromatids

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19
Q

Frequency of recombination =

A

total n# of recombinant gametes / total n# of parental gametes x 100/1

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20
Q

Recombinant frequencies can’t be greater than:

A

50%

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21
Q

The further apart genes are, the closer or further the recombination frequency gets to 50%

A

Closer

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22
Q

Relative position and physical position are or are not the same

A

are not necessarily the same

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23
Q

mu =

cM =

A

map units

centimorgans

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24
Q

1mu or 1cM is defined as:

A

the distance between genes for which 1 product of meiosis out of 100 is recombinant

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25
Q

1cM = recombination frequency of __%

A

1%

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26
Q

If all progeny of a test cross have EQUAL amounts of recombinant and nonrecombinant then is..

A

Independent assortment on different chromosomes

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27
Q

If all progeny of a test cross do NOT have equal amounts of recombinant and nonrecombinant then…

A

recombination is occuring on the same chromosome

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28
Q

Why is genetic mapping not efficient. What is more efficient

A
  • several 2-point crosses have to be carried out
  • double crossovers are missed
  • three-point test cross is more efficient
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29
Q

In recombinant chromosome resulting from double crossing what gene(s) are altered

A

Only the middle gene is altered

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30
Q

linkage group =

A

chromosome

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31
Q

Crossing over occurs how many times in a chromosome

A

1-3 times

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32
Q

Frequency of progeny for parental type, for single crossing over and double crossing over types

A

parental type = highest number
single crossing over = medium number
double crossing over = lowest number

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33
Q

Frequency of progeny for parental type, for single crossing over and double crossing over types

A

parental type = highest number
single crossing over = medium number
double crossing over = lowest number

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34
Q

To determine the gene order in a three-point cross:

A

compare the highest number (nonrecomninant progeny) and the lowest number (double-crosing over). They should be alike in 2 characteristics and differ in 1 characteristic. This different one is encoded by the middle gene

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35
Q

Expected frequencies of double crossing over =

A

(recombinant f x recombinant f ) x total gametes

36
Q

Interference=

% expected of double crossover progeny were not observed because of interference

A

1 - Coefficient of coincidence

37
Q

Interference=

A

1 - Coefficient of coincidence

38
Q

I =0
I = 1
I <1

A

I =0 no interference (equal expected and observed)
I = 1 complete interference (no observed db cross)
I <1 fewer recombinants that expected

39
Q

each meiocyte produces:

A

a linear array of 8 ascospores called an octad (octad of 4 spore pairs)

40
Q

Why cant centromeres be mapped

A

because they show no heterozygosity (variation)

41
Q

However in ______ you can map the centromere

A

Fungi

42
Q

Centromere mapping involves:

A

estimating the distance from a locus to the centromere

43
Q

What are the 2 patterns of alleles observed in the tetrad or octad

A

4:4 or 2:2:2:2

44
Q

How do you get the 4:4 allele pattern

A

First division segregation (M1 pattern). Arises when there is no crossing over between the gene and the centromere

45
Q

How do you get the 2:2:2:2 allele pattern

A

Second division segregation (M2 pattern). Arises when there is a crossover between the gene and teh centromere

46
Q
  • There are __ different spore arrangements/patterns from the 4:4 and 2:2:2:2 allele pattern
  • What are they?
  • What ones are Recombinants
  • How do they arise
A 
.Six
AAAAaaaa 
aaaaAAAA
AAaaAAaa (recombinant)
aaAAaaAA (recombinant)
AAaaaaAA (recombinant)
aaAAAAaa (recombinant)

Arise as the centromeres attach to the spindle at random

47
Q

How to calculate map distance of gene from centromere?

Very Important

A

Sum of the total of 2nd division (recombinants) / total Octads x100/1

This tells us that a crossover occurs in _% of meioses

Divide by 2 to get the map distance as half of the products of meiosis didn’t recombine

48
Q

Crossing over is a ___ and ____ process of chromatids

How was this found out?
The Harlequin chromosomes also showed this…

A

break and rejoining.
Found out by McClintock & Creighton using ‘marked’ chromosomes in maize: segment and knob- all recombinants had either the segment OR the knob

Tease and Jones - the harlequin chromosomes. Corissing over between light and dark stained non-sister chromatids, showed there is a physical exchange of chromatid segemts

49
Q

What did the Harlequin Chromosomes show?

A

Tease and Jones. Showed that crossing over occured at the FOUR CHROMATID STAGE, by proving that chiasmata were the crossing over site.

  • Observed chromosomes at diakinesis (prophase 1)
  • Only possible for tetrads to contain FOUR dfferent allele combinations if crossing over occurs at the 4 chromatid stage
50
Q

Multiple crossovers can include more/less/same than two chromatids

A

Multiple crossovers can include MORE than 2 chromatids

51
Q

Double crossover can involve THREE chromatids. This means______, not just _______, chromatids can cross.

A

non-adjacent, adjacent

52
Q

Crossing over can only occur between __ chromatids at any one time.

A

2

53
Q

What does polyethylene glycol do?

A

Fuse the membrane of a human fibroblast and mouse tumor cell

54
Q

What is a heterokaryon?

A

A hybrid cell that contains 2 nuclei

55
Q

What is somatic cell hybridization

A

the fusion of different cell types

56
Q

In ahuman-mouse comatic cell hybrid who’s chromosomes are lost

A

Humans

57
Q

In situ hybridisation is a method for:

A

Determining the chromosomal location of the gene through molecular analysis.
can be used for diagnostic purposes

58
Q

How does In situ hybridization work?

A
  • Require a probe thats single stranded, fluorescent and complementary for the gene.
  • You denature the target chromosome so it becomes single stranded
59
Q

What chromosome is associated with Down Syndrome

A

21

60
Q

What is Philadephia chromosome

A

In chronic myelogenous leukemia (CML) there is a translocation between chromosome 9 and 22

61
Q

What does CML stand for

A

Chronic myelogenous leukemia

62
Q

What are genetic markers?

A

Are variable genes with easily observable phenotypes (blood types, seed shape)

63
Q

Types of DNA markers (x4)

A

Minisatellite marker: based on variation in the number of tandem repeats 15-100 bp long

Microsatellite markers: based on variation in the number of a 2-6 bp sequence

Both loci have the same repeat unit just different number of repeats

Single nucleotide polymorphism (SNPs): are positions in the genome where people differ in a single nucleotide base

Restriction fragment length polymorphism (RFLPs) is a SNP that alters a restriction enzyme recognition site

64
Q

What method/approach was used in the discovery of the genes responsible for Huntingtons disease

A

Linkage analysis using DNA markers

65
Q

What are the 2 type of chromosomal mutations

A

structural and number

65
Q

What are the 2 type of chromosomal mutations

A

structural and number

66
Q

Changes in chromosomal number are refereed to as

A

polyploid changes

66
Q

Changes in chromosomal number are refereed to as

A

polyploid changes

67
Q

Structural mutations involve…

A

novel sequence rearrangements within 1 or more DNA molecule

67
Q

Structural mutations involve…

A

novel sequence rearrangements within 1 or more DNA molecule

68
Q

Why are chromosomal mutations important x5

A
  • understand how genes work together
  • insights into meiosis and chromosome architecture
  • tools for genomic manipulation
  • cause of genetic diseases
  • insights into evolutionary processes.
68
Q

Why are chromosomal mutations important x5

A
  • understand how genes work together
  • insights into meiosis and chromosome architecture
  • tools for genomic manipulation
  • cause of genetic diseases
  • insights into evolutionary processes.
69
Q

Types of chromosomal mutations x3

A
  • loss of genetic material
  • gain of genetic material
  • relocation of genetic material
69
Q

Types of chromosomal mutations x3

A
  • loss of genetic material
  • gain of genetic material
  • relocation of genetic material
70
Q

What causes loss of genetic material (x2)

A
  • deletion

- missing chromosome

70
Q

What causes loss of genetic material (x2)

A
  • deletion

- missing chromosome

71
Q

what causes a gain in genetic material (x2)

A
  • duplication

- extra chromosome

71
Q

what causes a gain in genetic material (x2)

A
  • duplication

- extra chromosome

72
Q

What causes relocation of genetic material (x2)

A
  • Translocation

- inversion

72
Q

What causes relocation of genetic material (x2)

A
  • Translocation

- inversion

73
Q

How do you form a deletion?

A

A chromosome segment can be lost

73
Q

How do you form a deletion?

A

A chromosome segment can be lost

74
Q

How do you form a duplication?

A

a section can be doubled

84
Q

How do you form a duplication?

A

a section can be doubled

85
Q

Haplotypes

A
  • determine gene position

- combination of alleles that are located closely together on the same chromsome ( often inherited together)

Biosci 202 (3 decks)

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