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G and H > Mendelian Genetics I and II > Flashcards

Mendelian Genetics I and II Flashcards

week 3 and 4

1
Q

allele

A

different genes located on same locus

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2
Q

what were the parameters of mendels pea experiment?

A

Traceable experiment system (controlled)

Looked for discrete, mutually exclusive traits.

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3
Q

What did the pea expeirment show?

A

dominance

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4
Q

How was dominance displayed?

A

Crossed: pure breeding, homozygous (P) talls with pure breeding shorts.

F1 = tall, F2 = 3:1 phenotype ration

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5
Q

Law of segregation

A

For any trait, pair of genes of each parents separate and are packaged into separate gametes = only one gene from each parent passes to offspring

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6
Q

locus

A

position gene occupies within a segment of a genome

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7
Q

co-dominance

A

both alleles fully expressed

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8
Q

incomplete domiance

A

Heterozygous phenotypically blend of homozygous dominant and homozygous recessive E.g red snap dragons

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9
Q

What is F1?

A

first generation offspirng from Parental generation (P)

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10
Q

What were the major conclusions of Mendels experiment?

A

Genes have multiple forms (alleles), T = tallness, t = shortness.

Each organism posses 2 genetic factors inherited from both parents

Gene may have one of two distinct types

One is dominant and determines the phenotype

Alleles separate with equal probability into gametes

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11
Q

What is the Chi-square test?

A

statistical test that determines whether the observed distribution of individual phenotypic categories is as predicted or occurs by chance.

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12
Q

Process for Chi-Square test:

A

1- record observed organisms in each phenotypic class = O

2- calculate expected values of each phenotypic class on basis of ratio = E

3- d (difference)= O-E

4= square d and divide by E in that phenotypic class.

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13
Q

What does a Chi-Square of O indicate?

A

no difference

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14
Q

What is the phenotypic ratio of a Dihybrid cross-breed

A

9: 3: 3: 1,
3:1 for single traits

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15
Q

What is the genotypic ratio for a Dihybrid cross-bredd?

A

: 1:2:1:2:4:2:1:2:1

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16
Q

What is Independent Assortment?

A

Random arrangement of homologous chromosomes pairs in metaphase I of Meiosis causing 2 different genes to randomly assort their alleles during gamete formation.

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17
Q

What is the exception to Mendle’s second law?

A

Some genes show linkage (inherited as single-unit from same chromosome).

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18
Q

How does meiotic recombination effect inheritance?

A

Alleles would otherwise always be inherited together.

Alleles on the same chromosome are partitioned into different gametes.

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19
Q

When will gene pairs assort independently? (2 ways)

A
  1. located on different chromosomes
  2. located far apart on the same chromosome
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20
Q

What is the probability of 2 genes crossing over proportional to?

A

Probability of 2 genes crossing over is proportional to: their distance apart on the chromosome

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21
Q

2 genes are linked if the show

A

Less than 50% recombinants relative to parental genotypes.

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22
Q

What is a test cross?

A

Dominant phenotype vs homozygous recessive organism = determine dominant parent genotype.

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23
Q

How is test cross completed?

A

Dihybrid cross with unknown dominant (home or hetero) and homozygous recessive.

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24
Q

If the result of the test cross shows: all offspring with dominant phenotype….

A

homozygous dominant genotype

25
Q

If the result of the test cross shows: mix of dominant and receive in EQUAL proportions….

A

heterozygous genotype (no-linkage, 1:1:1:1 ration)

26
Q

If the result of the test cross shows: mix of dominant and receive in UNEQUAL proportions….

A

heterozygous genotype, linkage (#parental haplotypes > # recombinant haplotypes)

27
Q

What is Epiostasis?

A

Alleles in 1 gene mask phenotypic effects of another

28
Q

Pleiotropy

A

1 gene may contribute to more than one visible characteristic

29
Q

What is the general format for mutation nomenclature?

A

prefix–> position –> reference base –> new base

30
Q

Allelles A and B are inhherited…

A

together

31
Q

Alleles B and C are inherited…

A

equal chance of together or not

32
Q

alleles a and b are inherited..

A

frequently, together

33
Q

Alleles b and c are inherited…

A

equal chance of together or not

34
Q

Assorted independently only if … why?

A

located on different chromosomes or far apart on the same chromosome

Because: The closer two genes are = the less likely cross-over will occur in meiosis.

35
Q

What is a human example of Epistasis?

A

H Antigen and Bombay Phenotype

AB of ABO locus add different terminal sugars to RBCs

Hh = bloody type O REGARDLESS of alleles they carry at ABO

36
Q

What does co-dominance, incomplete dominance and episatsis all have in common?

A

They are allelic combinations that do not exhibit standard dominant/recessive relationships.

37
Q

What are the three different ways mutational events can lead to phenotypic biochemical changes?

A

Changes in coding region of a gene

Changes in non-coding region

Changes in regulator sequences

38
Q

What is the result of a change in a coding region of a gene and an example?

A

Result: altered protein sequence, may not retain some function

e.g. cystic fibrosis

39
Q

What is the result of changes in non-coding region and example?

A

Result: failure for correct splicing

e.g collagen disorder (osteogenesis imperfecta)

40
Q

What is the result of changes in regulatory sequences and example?

A

Result: incorrect or failure of gene expression

e.g. deletion of b-globin Locus Control region (LCR) = B-thealassemia

41
Q

What are the two proposed reasons for why some mutations are dominant and some are recessive?

A

Recessive mutations affect enzymes

Dominant mutations affect structural proteins

42
Q

What are the four classes of gene mutations?

A

Base Subistitions
Deletions
Insertions
dynamic mutations

43
Q

What are base-substitutions and what are the 3 types (and consewunces of these types)

A

SINGLE BASE change at replication of DNA repair

Synonymous (silent)

Missense (change amino acid structure)

Nonsense (change protein structure)

44
Q

Dynamic mutations

A

Tandem repeats that change size following DNA replication

45
Q

How are missense mutations denoted? and example.

A

by a three-letter abbreviation for wild-type amino acid, position number, three letter abbreviation for mutated amino acid

e.g Cys88Tyr
cystine at position 88, change into tyroisne

46
Q

How are nonsense mutations denoted?

A

three-letter abbreviation for the wild type amino acid – position number – then a Ter or *, signifying the stop codon

e.g. Lys385Ter or Lys385*

47
Q

How are insertion mutations named and example.

A

nucleotide number of the last wild type nucleotide before the insertion – ins
g.5384_5385insC

48
Q

How are deletion mutations named?

A

nucleotide number of the first
deleted nucleotide - del (short for deletion)

g.6184del

49
Q

What is a hybrid cross?

A

two separate genes considered = 9 different genotypic combinations

produces a dihybrid

50
Q

Dihybrid vs monohybrid cross

A

monhybrid = AaxAa (3 possible genotypes)

Dihybrid cross= AaBb x AaBb (9 possible genotypes)

51
Q

What stage of division is dihybrid crosses occurring and why?

A

Meiosis I
- 4 different chromosomes from diploid cell

52
Q

What are the three steps of PCR amplification?

A

Denaturation= two strands of DsDNA separed as weak forces between helix are disrupted

annealing: binding primers to upstream and downsteam region that will be amplified

extenstion: Taq DNA polymerase adds dnTPs from 5-3 direction

53
Q

How are an individual’s STR alleles analysed?

A

1- DNA estracted from individual
2- STRs amplifed
3- STRS tagged with a fluroescent makrers
4- capilary electrophrises (laser excites fluroesecnt dyes)

54
Q

Describe the features of Autosomal dominant pedigrees.

A

Multiple generations are affected
male and female equally likely
affected person has one affected parent

55
Q

Describe the features of autosomal recessive inheritance.

A

All offspring are carriers if a parent is affected
often skips generations

56
Q

Describe X-linked recessive inheritance

A

Knight’s move
affects mostly males
never transmitted from father to son

57
Q

Describe the features of X-linked dominant inheritance.

A

2:1 female: male
father to daughter

58
Q

Crossing over

A

occurs in Prophase 1 and sees parental chromosomes swap genetic material. The probability of crossing over is proportional to the distance of genes apart.

59
Q

Describe mitochondrial inheritance

A

only females can pass on disease
but male and female can develop

G and H (16 decks)

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