Lecture 4, 5, 6, 7 & 8 Flashcards Preview

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

Flashcards in Lecture 4, 5, 6, 7 & 8 Deck (85):
1

Locus

the specific place on a chromosome where a gene is located

2

each individual has 2 alleles, however...

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

3

Mitosis (x4)

-1 division
-2 identical daughter cells
-Somatic cell
-For growth and repair

4

Meiosis (x3)

-2 divisions
-4 haploid daughter cells
-for the production of sperm/egg/gametes

5

heteromorphic chromosomes

different looking chromosomes

6

What did the Datura plants show

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

7

What did Morgans data show

That linked genes in a dihybrid may be present in 2 configurations:
-Cis configuration
-Trans configuration

8

Cis Configuration

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

9

Trans Configuration

(opposite) the 2 dominant alleles are on different homolog

10

Result from dihybrid crosses & linkage (ratios)

-2 equally frequent NON-RECOMBINANT classes totaling GREATER than 50%

-2 equally frequent RECOMBINANT classes totalling LESS THAN 50%

11

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

-further apart = more crossing over & higher recombination number
-closer together = less crossing over, very low recombination number

12

Morgan suggested that recombination is bought about by...

Chiasma formation

13

When does Chiasma formation occur

during zygotene/pachytene of meiotic prophase 1

14

What is Chiasma

Sites of crossing over

15

Morgan's Data

homozygous recessive X homozygous dominant

=heterozygous

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

16

INTERchromosomal recombination

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

17

INTRAchromosomal recombination

Mediated by CHIASMA FORMATION where the RECOMBINANT classes are LESS frequent.
p: >1/4
p: >1/4
r: < 1/4
r: <1/4

18

Bivalents are...

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

19

Frequency of recombination =

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

20

Recombinant frequencies can't be greater than:

50%

21

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

Closer

22

Relative position and physical position are or are not the same

are not necessarily the same

23

mu =
cM =

map units
centimorgans

24

1mu or 1cM is defined as:

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

25

1cM = recombination frequency of __%

1%

26

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

Independent assortment on different chromosomes

27

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

recombination is occuring on the same chromosome

28

Why is genetic mapping not efficient. What is more efficient

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

29

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

Only the middle gene is altered

30

linkage group =

chromosome

31

Crossing over occurs how many times in a chromosome

1-3 times

32

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

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

33

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

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

34

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

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

35

Expected frequencies of double crossing over =

(recombinant f x recombinant f ) x total gametes

36

Interference=
(% expected of double crossover progeny were not observed because of interference)

1 - Coefficient of coincidence

37

Interference=

1 - Coefficient of coincidence

38

I =0
I = 1
I <1

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

39

each meiocyte produces:

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

40

Why cant centromeres be mapped

because they show no heterozygosity (variation)

41

However in ______ you can map the centromere

Fungi

42

Centromere mapping involves:

estimating the distance from a locus to the centromere

43

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

4:4 or 2:2:2:2

44

How do you get the 4:4 allele pattern

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

45

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

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

46

-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

.Six
AAAAaaaa
aaaaAAAA
AAaaAAaa (recombinant)
aaAAaaAA (recombinant)
AAaaaaAA (recombinant)
aaAAAAaa (recombinant)

Arise as the centromeres attach to the spindle at random

47

How to calculate map distance of gene from centromere?

(Very Important)

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

Crossing over is a ___ and ____ process of chromatids

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

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

What did the Harlequin Chromosomes show?

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

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

Multiple crossovers can include MORE than 2 chromatids

51

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

non-adjacent, adjacent

52

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

2

53

What does polyethylene glycol do?

Fuse the membrane of a human fibroblast and mouse tumor cell

54

What is a heterokaryon?

A hybrid cell that contains 2 nuclei

55

What is somatic cell hybridization

the fusion of different cell types

56

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

Humans

57

In situ hybridisation is a method for:

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

58

How does In situ hybridization work?

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

59

What chromosome is associated with Down Syndrome

21

60

What is Philadephia chromosome

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

61

What does CML stand for

Chronic myelogenous leukemia

62

What are genetic markers?

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

63

Types of DNA markers (x4)

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

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

Linkage analysis using DNA markers

65

What are the 2 type of chromosomal mutations

structural and number

65

What are the 2 type of chromosomal mutations

structural and number

66

Changes in chromosomal number are refereed to as

polyploid changes

66

Changes in chromosomal number are refereed to as

polyploid changes

67

Structural mutations involve...

novel sequence rearrangements within 1 or more DNA molecule

67

Structural mutations involve...

novel sequence rearrangements within 1 or more DNA molecule

68

Why are chromosomal mutations important x5

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

68

Why are chromosomal mutations important x5

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

69

Types of chromosomal mutations x3

-loss of genetic material
-gain of genetic material
-relocation of genetic material

69

Types of chromosomal mutations x3

-loss of genetic material
-gain of genetic material
-relocation of genetic material

70

What causes loss of genetic material (x2)

-deletion
-missing chromosome

70

What causes loss of genetic material (x2)

-deletion
-missing chromosome

71

what causes a gain in genetic material (x2)

-duplication
-extra chromosome

71

what causes a gain in genetic material (x2)

-duplication
-extra chromosome

72

What causes relocation of genetic material (x2)

-Translocation
-inversion

72

What causes relocation of genetic material (x2)

-Translocation
-inversion

73

How do you form a deletion?

A chromosome segment can be lost

73

How do you form a deletion?

A chromosome segment can be lost

74

How do you form a duplication?

a section can be doubled

84

How do you form a duplication?

a section can be doubled

85

Haplotypes

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