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Genetics & Molecular Biology > Mendelian Genetics > Flashcards

Mendelian Genetics Flashcards

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1
Q

Define Diploid

A

number of chromosomes in the somatic (body) cells
- in humans the diploid number is 46

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2
Q

Define Haploid

A

A single set chromosomes present in the egg & sperm of animals, egg & pollen of plants and in stable/transient life cycle forms of other organisms

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3
Q

Define Chromosome

A

self-replicating structures of cells that carry their nucleotide sequences in an literal array of genes

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4
Q

Define Karyotype

A

the entire chromosomes complement of an individual or cell as seen during the mitotic metaphase

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5
Q

Define Allele

A

1 of the different forms of a gene or DNA sequence that can exist at a single locus

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6
Q

Define Genotype

A

the actual alleles present in an indvidual

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7
Q

Define Phenotype

A

Observable characteristics of an organism

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8
Q

Define Trait

A

Any detachable phenotypic variation of particular inherited character

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9
Q

Define Gene

A

the fundamental physical and functional unit of heredity , which carrier info from 1 generation to the next, a segment of DNA, composed of a transcribed region and a regulatory sequence that makes transcription possible

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10
Q

Define Zygote

A

the single cell with 46 chromosomes resulting from the fertilisation of an egg by a sperm

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11
Q

Define Homozygous

A

Having 2 of the same alleles at a given locus on a pair of homologous chromosomes

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12
Q

Define Heterozygous

A

having 2 different alleles at a given locus on a pair of homologous chromosomes

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13
Q

What are the desirable characteristics of plants ?

A
  • can be grown in large quantities
  • produce a large number of offspring - seeds
  • relatively short generation times
  • many have male & female reproductive
  • easy to control which individuals mate
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14
Q

Describe Mendel’s Experimental Methods

A
  • hand-pollinated flowers using painbrush
  • he could snip the stamens to prevent self-pollination
  • covered each flower with a cloth bag
  • he traced traits through several generations
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15
Q

What are the 8 pea plant traits ?

A

seed shape
seed colour
pod shape
pod colour
seed coat colour
flower position
plant height
flower colour

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16
Q

Describe Mendel’s well-ordered experimental plan

A
  • used characters that were well-defined alternative traits –> purple/ white flowers - spherical/wrinkled peas
  • were true-breeding –> only form present for many generations - parent generations
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17
Q

What are progeny from the cross of P parents called ?

A

the first filial generation (F1)

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18
Q

Define Monohybrid cross

A

cross involving a single trait –> flower colour

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19
Q

Define Dihybrid cross

A

cross involving 2 traits –> flower colour & plant height

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20
Q

What is Mendel’s 1st Law of Inheritance ?

A
  • Law of unit characters
  • Every trait is controlled by at least 1 pair of genes
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21
Q

Describe the Law of Assortment

A

alleles of different genes assort into gametes independently of each other

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22
Q

Describe the Law of Domimance

A
  • one of the genes in the pair may be dominant over the other which is recessive
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23
Q

Describe the Law of Segregation

A
  • the genes pair separate when gametes are formed
  • only 1 of each gene pairs is represented in each of the gametes
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24
Q

Describe the F1 monohybrid cross results

A
  • heterozygous X heterozygous
  • 25% homozygous dominant RR
  • 50% Heterozygous Rr
  • 25% Homozygous Recessive rr
  • offspring is called F2 generation
  • genotypic ratio = 1:2:1
  • phenotypic ratio = 3:1
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25
Q

Define Codominance

A

2 alleles are expressed in heterozygous individuals
- example = blood type

26
Q

What are the 2 kinds of probability ?

A
  • empirical probability
  • theoretical probability
27
Q

Define Empirical Probability

A
  • its calculated by counting the number of times that event occurs and dividing it by the total number of times than event could have occurred
28
Q

Define Theoretical Probability

A
  • its calculated & reflects the number of times an even is expected to occur relative to the number of time it could possibly occur
29
Q

Describe Pedigrees

A
  • family trees
  • show phenotype segregation in several generations of related individuals
30
Q

Define Single Gene Disorders

A
  • changes/mutations in the DNA sequence of one gene
31
Q

What are some subtypes of single gene disorders ?

A
  • autosomal dominant
  • autosomal recessive
  • X-linked dominant
  • X-linked recessive
  • Y-linked
32
Q

Describe Autosomal Dominance Inheritance

A
  • Aa & AA are affected
  • all affected individual should have an affected parent
  • both sexes should be equally affected
  • Example = Huntington’s Disease
33
Q

Describe Huntington’s Disease

A
  • caused by a triple repeat expansion in the Huntingtin gene
  • occurence = 1/100,000
  • symptoms = personality change, progressive chorea, dystonia & dementia
34
Q

Describe Autosomal Recessive Inheritance

A
  • only aa are affected, Aa are carriers
  • usually no previous family history
  • inbreeding increases the chance of observing an autosomal recessive condition
  • example = cystic fibrosis
35
Q

Describe Cystic Fibrosis

A
  • caused by a mutation in the CFTR gene
  • 1/25 people are carriers
  • Symptoms = chronic obstruction of the airway, shortness of breath, malnutrition & infertility
36
Q

Define Wild Type Alleles

A

most common allele in population >99%

37
Q

Define Mutant allele

A

may produce a phenotype different from that of the wild-type allele

38
Q

Describe Incomplete Dominance

A
  • when 2 traits ‘meet in the middle’ instead of showing a definite dominant/recessive relationship
  • Red X white snapdragons = 1:2:1 ratio of Red:pink:white flowers
39
Q

Define Pleotropic alleles

A

single alleles with more than 1 distinguishable phenotypic effect
–> colouration pattern & crossed eyes in siamese cats = caused by the same allele

40
Q

Define Epistasis

A
  • alleles of 1 gene cover up or alter expression of alleles of another gene
  • example = several genes determine coat colour in Labrador retriever
41
Q

Describe how coat colour is determined in dogs

A
  • a single dominant allele at the first locus influences the expression or allele at a second gene locus
  • Black Labs = BBEE, BBEem BbEe
  • Chocolate Labs = bbEE, bbEe
  • Yellow Labs with Dark skin = BBee or Bbee
  • Yellow labs with pale skin = bbee
42
Q

In what scenarios does epistasis occur ?

A
  • whenever 2 or more loci interact to create new phenotypes
  • whenever an allele at 1 locus masks the effects
  • whenever an allele at one locus modifies the effect of ales at 1 or more other loci
43
Q

Describe how temperature effects evening primrose

A
  • mutations affected by temp are conditional or temperature-sensitive mutations
  • evening primrose produces red flowers at 23 degrees and white flowers at 18
44
Q

Describe how temperature effects Himalayan Rabbit

A
  • has black fur on its extremities due an ancestral trait
  • temperature sensitive tyrosinase genes which controls fur pigmentation
  • natural selection has favoured a gene that allows for a darker pigmentation which activates in low temperatures - chaining the individual rabbits phenotype to fit the climate
  • black fur absorbs light & solar heat, keeping that part of the rabbit which has dark fur warmer
45
Q

Define penetrance

A

proportion of individuals in a group with a given genotype that actually show the expected phenotype

46
Q

Define Expressivity

A

Degree of expression of a given trait or combination of traits that is associated with a gene
- condition may have severe or mild symptoms

47
Q

Define Monoecious

A
  • example = corn & peas
  • every diploid adult has both male & female reproductive structures
48
Q

Define Dioecious

A
  • example = other plant & most animals
  • some individual produce only male gametes, other produce only femlae gametes
49
Q

What are examples Sex Chromosomal Disorders ?

A
  • Turner’s syndrome - XO, monosomy X
  • Triple-X syndrome - XXX
  • Jacob’s Syndrome - XYY
50
Q

Describe Sex Determination

A
  • some XY individuals lack a small portion of Y chromosomes are phenotypically female
  • some XX individuals with a small piece of the Y chromosome are male
  • fragment contains the maleness-determining gene
  • SRY = Sex-determining Region on the Y chromosome
  • SRY codes for a functional protein - protein present = testes develop
51
Q

Describe X chromosome inactivation

A
  • Anhidrotic ectodermal dysplasia
  • EDA gene which are inherited in an X-linked recessive pattern
  • Małe hemizygotes = no teeth, sparse hair & no sweat glands
  • female hemizygotes = random patterns of tissue, with/without sweat glands
52
Q

Describe Sex Linked Inheritance in relation to Pedigrees

A
  • phenotype appears much more often in males than female
  • male with mutation can only pass it to his daughters
  • daughters who receive 1 mutant X are heterozygous carriers
53
Q

Describe X-Linked Dominant Inheritance

A
  • females and males are affected
  • no cases of male to male transmission
  • examples = Focal Dermal Hypoplasia & Familial Hypophosphatemic rickets
54
Q

Describe X-Linked Recessive Inheritance

A
  • affected males have normal sons & carrier daughters
  • affected females will have 50% chance that their child inherits the disorder (sons) or is a carrier (daughters)
  • examples = Colour blindness & Haemophilia
55
Q

Describes Y-Linked Inheritance

A
  • only males affected
  • no cases of male –> female transmission
  • usually results in infertility
  • Y chromosome is relatively small and contains few genes so there are relatively few y-linked disorders
56
Q

Describe Maternal Inheritance

A
  • a mother with mitochondrial DNA gene mutation will pass abnormal gene to all her children
  • children will all be affected with varying degrees of severity
57
Q

Define Homoplasmic cells

A

homoplasmic cells = cells which only contain normal mtDNA

58
Q

Define Heteroplasmic cells

A
  • people with a maternally inherited disease and their maternal relatives usually have heterplasmic cells –> some of the mtDNA is normal and some aren’t - containing mutations
59
Q

Describe Mosaicism

A
  • somatic mosaicism = occurrence of 2 genetically distinct populations of cells within an individual - derived from a post zygotic mutation
  • may only affects a portion of the body & isn’t transmitted to the progeny
60
Q

Describe Genomic Imprinting

A
  • for imprinted genes only 1 working copy is inherited - as opposed to 2 - 1 from each parent
  • depending on the gene one gene copy is epigenetically silenced
  • silencing usually happens through the addition of methyl groups during gamete formation

Genetics & Molecular Biology (13 decks)

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