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biology > principles of inheritance and variation > Flashcards

principles of inheritance and variation Flashcards

1
Q

Entire body of molecular bio-contributions from

A

Watson
Crick
Nirenberg
Khorana
Kornbergs
Benzer
Monod
Brenner

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2
Q

indian breed through artificial selection and domestication from ancestral wild cows

A

Sahiwal cows in punjab

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3
Q

mid-19th century

A

headway was made in the understanding of inheritance

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4
Q

period of Mendel’s hybridisation experiments on pea plants

A

7 years
1856-1863
and proposed law of inheritance in living organisms

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5
Q

what gave credibility yo the data mendel collected

A

statsitical analysis an dmathematical logic were apploied

large sampling size

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6
Q

why mendel’s result pointed to general rules of inheritamce rather than being unsubstantiated ideas

A

experiments on successive generation of his test plants

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7
Q

mendel investigated characters in pea plants tahat were

A

manifested as two opposing traits

-allowed him to set up a basic framework of rules governing inheritance

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8
Q

mendel conducted ____________ experiments using several _________

A

artificial pollination/cross pollination

true-breeding pea lines

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9
Q

true-breeding line

A

having undergone continuous self-pollination
shows stable trait inheritance
and expression for several generations

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10
Q

how many true-breeding plant varities did mendel select as pairs which were similar, except in one character with contrasting traits

A

14

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11
Q

contrasting traits studied by mendel in pea

A
  1. stem height-tall/dwarf
  2. flower color- violet/white
  3. flower position-axial/terminal
  4. pod shape-inflated/constrcited
  5. pod color-green/yellow
  6. seed shape-round/wrinkled
  7. seed color-yellow/green
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12
Q

how mnay pairs of contrasting characters in pea plants were studied by mendell in his experiments

A

7

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13
Q

humans knew as early as _____ that one of the causes in variation was hidden in ____

A

8000-1000 BC
sexual rep

-exploited variations naturally present and selectively bred and select organisms with desired characters

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14
Q

first geenticist/father of genetics

A

mendel

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15
Q

what cntributed to the succes of mendel

A

consideration of one character at one time

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16
Q

sum up the results seen from f1 and f2 gen

A

only one of parental traits was expressed in f1
f2-both traits expressed in propotion 3:1

the contrasting traits did not show any blending at either f1 or f2

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17
Q

removal of anthers

A

emasculation

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18
Q

what did mendel proposed based on his observations

A

something was being stably passed down, UNCHANGED from parent to offspring thru gametes over succesive generations

-these are factors

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19
Q

unit of inheritance

A

genes-has info to express a particular trait in an organism

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20
Q

alleles

A

genes that code for a pair of contrasting traits

slightly different forms of the same gene

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21
Q

mendel proposed that in true breeding

A

alleles are homozygous

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22
Q

as mendel found the phenotype of F1 heterozygote Tt to be exactly like TT of parent, he proposed that:

A

in a pair of dissimilar factors, one dominated the other

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23
Q

monohybrid

A

to be heterozygous for genes controlling one character
eg Tt

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24
Q

cross between TT and tt is a

A

monohybrid cross

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25
Q

from the observation that the reccessive trait is expressed with no blending in F2. We can infer that

A

during meiosis the alleles of the parental pair segregate and only one allele is transmitted to a gamete

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26
Q

punnet square-developed by

A

Reginald C. Punnett

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27
Q

genotypic and phenotypic ratio from the selfing of F1 plants

A

ge 1:2:1
phe 3:1

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28
Q

F1 plants produced gamets of the geneotype T or t in

A

equal proportion

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29
Q

mendel self pollinated the F2 plants and found that

A

dwarf f2 plants continued to produce dwarfs in f3 and f4…he concluded that genotype of dwarfs-tt

30
Q

mendels two general rules

A

principles or laws of inheritance:
1. first law or law of dominance
2. 2nd law/ law of segregation

31
Q

law of dominance

A
  1. characters are controlled by discrete units called factors
  2. factors occurs in pairs
  3. in dissimilar pair of factors-one is dominant ove rthe other
32
Q

law of dominance explains

A
  1. expression of only one of parental characters in a monohybrid cross in F1
  2. expression of both in F2
  3. proportion of 3:1 obtained at F2
33
Q

law of segregation

A
  1. alleles do not show blending
  2. both characters are recovered in F2, tho one is not in F1
  3. during gamete formation, alleles segregate and only receives one of the two factors
  4. homo-all gametes similar
    hetero-two kinds of gametes each having one allele with equal proportion
34
Q

incomplete dominance- how was it discovered

A

when experiments on peas were repeated using other traits in OTHER plants

it was found that F1 had a phenotype that did not resemble either parents and was in between them

35
Q

incomplete dominance-example

A

inheritance of flower color in dog flower—snapdragon or Antirrhinum sp

truebreeding red flower: RR
true breeding white flower: rr

F1-Rr-pink

when F1 self pollinated:
F2 genotypic ratios: 1:2:1 red-pink-white
phenotypic ratios: 1:2:1 red pink white
BECAUSE R wasnt completely dominant over r

36
Q

co dominance

A

F1 gen resembles both parents

37
Q

ex of codominance

A

different types of rbc that determine ABO blood grouping in human

38
Q

ABO blood grping controlled by

A

gene I

39
Q

gene I function

A

plasma membrane of RBC has sugar polymers protude from its surface and the kind of sugar-controlled by gene

40
Q

how many alleles does gene I have

A

3
IA and IB are completely dominant over i

IA and IB-produce slightly different form of sugar
i-no sugar

41
Q

genotypic and phenotypic combinations of the alleles in gene I

A

6 different genotypes and 4 phenotypes

42
Q

ABO blood grping also provides a good example of

A

multiple alleles as 3 alleles govern the same character

43
Q

multiple alleles can be found only when

A

population studies are made

44
Q

Give and explain an example where a single gene product may produce more than one effect

A

Starch synthesis in pea plants is controlled by ONE gene

Which has two alleles B and b

BB: Starch synthesised effectively—large starch grains are produced
bb: starch synthesised less effectively—smaller starch grains

After maturation of seeds:
BB: round
bb: wrinkled

Heterozygous—round seeds so B seems to be dominant

But starch grains are of intermediate size in Bb seeds—alleles show incomplete dominance

45
Q

Dominance is not an

A

Autonomous feature of gene or the product it has info for

46
Q

Dominance depends on

A

The gene product and the production of a particular phenotype from this product

47
Q

Inheritance of two genes: Mendel crossed pea plants that has seeds with

A

Yellow, round with green, wrinkled
Result: yellow round- identical to those that he got with mono hybrid crosses

48
Q

F2 gen phenotypic ratio after self crossing F1 gen (all round yellow)

A

9:3:3:1 round yellow, round green, wrinkled yellow, wrinkled green

Yellow and green color segregated into 3:1 ratio so did round is to green as in mono hybrid cross

49
Q

Mendel published his work on inheritance of characters in

A

1865 but remain unrecognised till 1900

50
Q

Why mendel’s work wasn’t unrecognised until 1900

A
  1. Communication wasn’t easy
    and Work couldn’t be widely published
  2. His concept of genes as stable and discrete units that controlled expression of traits and, of the pair of alleles which did not blend with eachother wasn’t accepted as an explanation for continuous variation
  3. Approach of math in bio - was completely new and unacceptable
  4. Suggested that Factors were discrete units and couldn’t provide physical proof that they exist or say what they were made of
51
Q

in 1900 who independently rediscovered mendel’s work

A

De vries, Correns and von Tschermak

52
Q

in 1900 what else happened

A

due to advancements in microscopy-able to observe cell division-led to discovery of structures in the nucleus that appear to double and divide just before cell divisionn and they were called chromosomes

53
Q

chromosomes aka

A

colored bodies as they were visualised by staining

54
Q

in 1902

A

chromosomes movement has been worked out

55
Q

chromosomal theory of inheritance

A

Walter Sutton and Theodre Boveri

-noted that behaviour of chromosomes was parallel to the behaviour of genes and used chromosomal movement to explain Mendel’s laws

56
Q

chromosomea dn genes occur in

A

pairs

57
Q

the two alleles of a gene are located on

A

homologous site son homo chromosomes

58
Q

Sutton and Boveri argued that

A

pairing and seperation of a pair of chromosomes would lead to segregation of a pair of factors they caried

59
Q

Sutton united…

A

knowledge of chromomal segregation with Mendelian principles-chromosomal theory of inheritance

60
Q

Thomas Hunt Mogan

A

did experimental verification of chromosomal theory of inheritance

which led to discovering the basis for the variation that sex. rep. produced

61
Q

Why did morgan work with drosophila

A
  1. could be grown on simple synthetic medium in lab
  2. complete life cycle abt 2 weeks
  3. single mating-produce large no of progeny
  4. clear differentiation of sexes
  5. has many types of hereditary variations seen with low power microscope
62
Q

how did Morgan study sex-linked genes in drosophila

A

by carrying out several dihybrid crosses-similar to mendel

yellow bodied, white eyed with brown body, red eyed and intercrossed F1 progeny

the genes were on the X chrommo

63
Q

what did morgan observe

A
  1. when two genes in a dihybrid cross were on the same chromosome-proportion of parental gene combinations»than non-parental
  2. some genes-v tightly linked and others are loosely linked
    eg: genes white and yellow show 1.3% recombination white and miniature wing-37.2% recombination
64
Q

who coined linkage and recombination

A

morgan

linkage: to describe the physical association of genes on a chromosome

recom: describe the generation of non-parental gene combin

65
Q

Alfred Sturtevant

A

used frequency of recombination btwn gene pairs on same chromosomes as a measure of distance between genes and mapped their positin on chromosome

66
Q

genetic maps

A

used for sequencing whole genomes as in HUman genome sequencing project

67
Q

pleiotropy

A

where a single gene can exhibit multiple phenotypic expression

in most cases it is the effect of a gene on metabolic pathways which contribute towards different phenotypes

68
Q
A
69
Q
A
70
Q
A

biology (4 decks)

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