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Fundamental genetics > Exam 2 > Flashcards

Exam 2 Flashcards

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Biology 101 flashcards
1
Q

Allele

A
  • one or two alternative forms of a gene that arise by mutation and are found at the same place in a chromosome
  • wild type allele: normal allele (most common one in the population)
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2
Q

Loss of function mutation

A

-reduced productivity of gene product

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3
Q

Null Alelle

A
  • no productivity of gene function at all
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4
Q

Gain of function mutation

A
  • increased or extra productivity

- or does a new function

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5
Q

Neutral mutation

A
  • change to distinguish one allele from another

- no phenotypic change

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6
Q

Incomplete dominance

A
  • dominant allele is not fully expressed when recessive allele is present (blend of 2 colors)

Ex: pink flower offspring from red and white P gen

  P generation-> 1 RR=red x 1 rr=white
  F1 generation-> 4 Rr-> PINK
  F2 generation-> 1 RR:2Rr:1rr
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7
Q

Codominance

A
  • alleles work together, both are expressed or seen

Ex: white chicken with black speckles

  • MN blood types antigens on RBC
  • two alleles L^M and L^N
  • phenotypes:
    LMLM=M antigen x LNLN= N antigen
    LMLN= both antigens present, NOT BLENDEDi
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8
Q

Pleitropy

A
  • one gene that impacts several aspects of the overall phenotype
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9
Q

Epistasis

A
  • recessive epistasis
  • one gene is very dependent on another gene to allow the other gene to be expressed
  • 16 square Punnett

Ex: cross BbCc x BbCc
BB=black bb= brown cc=epistasis recessive

If has __cc ex: Bbcc it will be ALBINO
- Bb is the hypostatic, or hidden gene

  • 9:3:4 ratio
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10
Q

Penetrance

A
  • percent of individuals with a specific allele or genotype that we would expect
  • answers: yes OR no if you have the allele will you express the phenotype

Ex: if 45/50 people exhibit trait:
90% penetrance

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11
Q

Incomplete penetrance

A
  • genotype/allele does not always produce the expected phenotype
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12
Q

Expressivity

A
  • the degree of HOW MUCH of the phenotype you will display, how severe?
  • assume 100% penetrance (you will def express it)
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13
Q

Temperature effect

A
  • causes variability or expressivity
  • temperature sensitive allele

Ex: rabbits in the Himalayas produces dark fur at extremities less than 25 Celsius or less

Norm of reaction: range of phenotypes produced by a genotype in diff environment **

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14
Q

Thomas Hunt Morgan

A
  • first explained sex linked inheritance
  • found some traits were specific to sex
  • suggested that genes on the same chromosome segregated together and those closely linked were rarely subject to recombination

Ex: fruit flies in a male only have the X chromosome and it is dependent on whether or not they have white eyes

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15
Q

Sex chromosomes and pedigree analysis of them

A
  • genes are expressed by the X chromosome
  • females have 2 X chromosomes and males only have one an XY
  • males can not be carriers of the recessive allele can only be affected if have it and are more commonly affected than females
  • if father has the recessive allele any daughter will be at least a carrier Bc they receive one X from mom and one X from dad
  • if the daughters son is affected must have the recessive allele because only has ONE X the affected one
  • mom affects all sons with recessive allele and dad affects all daughters with recessive allele
  • although phenotypes appear to skip generations, they NEVER do
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16
Q

Autosomes

A
  • any chromosomes that are not sex chromosomes
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17
Q

3 types of sex inheritance

A

1) sex linked inheritance
- only on the X or Y chromosome
- Y-linked will affect ALL male offspring

2) sex limited inheritance
- in Autosomes both male and females have it
- “on” or “off” scenario, ONLY ONE SEX will express it (zero penetrance in other sex)
Ex: only female hormones will trigger lactating breasts, males will never trigger

3) sex influenced inheritance
- on Autosomes both males and females
- variation in how males and females will express the same gene
Ex: all people have body hair but males have much more

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18
Q

Genomic imprinting (Prader Willi/angelman syndrome)

A
  • occurs with autosomal genes
  • one copy of the gene from either mom or dad is silenced by cytosine methylation and the over gene is turned “on” or activated

Angelman Syndrome-> the mutated allele from mom is inherited (then turned off) and the father gene is already silenced through methylation causes excessive laughter

Prader Willi-> the mutated allele from father is inherited(then turned off) and the mom is already silenced through methylation causes excessive eating

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19
Q

Epigenetics

A
  • genome modification that doesn’t affect the DNA sequence but will affect the function
20
Q

Cytoplasmic Inheritance

A
  • genes are located in the cytoplasm (chloroplasts and mitochondria)
  • zygote will inherit nuclear genes from both parents, but all (most) cytoplasmic genes come from the mother
  • affected females will pass it on to all children (male/female)
  • males do not pass trait on to children
21
Q

Genetic maternal effect

A
  • genes/allele are passed on by both parent but phenotype is determined by the genotype of the mother
22
Q

Chromosomal sex determination

A
  • chromosome theory of inheritance->
23
Q

chromosome theory of inheritance

A
  • genes are located on chromosomes and chromosomes are substrate for gene segregation
24
Q

Henking

A
  • male insects had strange body in nuclei = X body
25
Q

McClung

A
  • male grasshoppers have a heterochromosome, female grasshopper cells had one more chromosome than males

X body=chromosome

Heteromorphic chromosomes-> distinction btw X and Y chromosomes

26
Q

Stevens

A
  • female mealworms have 20 large chromosomes
  • males have 19 large and 1 smaller one a Y
  • X and Y separate into different sperm cells, while all egg cells get single X
27
Q

Wilson

A
  • female butterflies have 2 X chromosomes

- males have one X chromosome

28
Q

Alfred H Sturtevant

A
  • Thomas Morgan’s student
  • generated the first map of chromosome based on the frequency of recombination
  • postulated that frequency can determine the physical distance separating the two genes on a chromosome
29
Q

frequency of recombination rules (high, low, etc)

A
  • if it is high genes are further spread, can undergo double crossovers if very far (appears the crossover never occurred)
  • if it is low genes are closer together, Thomas hunt Morgan said the closer together they are the less of a chance of recombination there is
  • frequency can not be >50% or =50% , if they are they are on different chromosomes
30
Q

Recombination frequency formula

A

= # of recombination progency / total # of progency x100

31
Q

Genetic maps

A
  • use recombination frequencies to make chromosome maps

- distances are in terms of map units (=1% recombination frequency) aka centimorgans (cM)

32
Q

Physical maps

A
  • chromosome maps based on physical distances (base pairs)
33
Q

Define Interference(pos, neg, complete) and formula to find it

A
  • when the crossover in one region affects the probability of a crossover in a nearby region
  • the closer the genes are together, the more interference there is (positive interference)
  • the further the genes are, the less interference there is (negative interference)
  • if interference is 1 you will have zero crossovers

1- coefficient of coincidence

34
Q

Coefficient of coincidence

A

COC= # of observed cross overs/# of expected cross overs x 100

  • get expected from data table
  • get observed by calculating probability of BOTHS DCO multiply those together then multiplying by total number of progeny
35
Q

Two types of Linkage

A

1) complete linkage
- occurs between the genes on a single pair of homologous chromosome, close together so crossing over(recombination) is very rare
- produces two genetically different parental gametes
- will not seperate according to THM (fruit fly body and wing shaped are linked genes 1:2:1 ratio instead of 9:3:3:1)

2) incomplete linkage
- occurs between two pairs of homologous genes that have 2 genes that are on same chromosome, but some distance apart so allows crossing over (recombination) btw nonsister chromatids
- produces two recombinant or crossover gametes and 2 parental gametes
- 4 sets 9:3:3:1

36
Q

Linkage groups

A
  • number of chromosomes in 1 set(n)
  • ALL THE GENES LOCATED ON THE SAME CHROMOSOME
  • significance of linked genes is that they are used as distant markers (determine linkage group and genetic map in humans)
  • distant markers can be tied together by intermediate markers to span further than 50cM

Ex: humans have 2n (2 sets of chromosomes)
N=23 so linkage groups = 23

Ex 2: drosophila fruit fly have 2n=4 pairs of chromosomes. N=4
Linkage groups=4

37
Q

Turner Syndrome

A
  • sex chromosome abnormality due to nondisjunction
  • females have only one copy of sex chromosome (XO)
  • 45 total chromosomes, X no Y
  • develop female because presence of X
  • do not undergo puberty
38
Q

Klinefelter Syndrome

A
  • sex chromosome abnormality due to nondisjunction
  • have XXY chromosomes, more than one X only one X is functional other is inactivated and becomes a Barr body
  • develops male because Y chromosome, but will have secondary female sex characteristics
  • enlarged breasts, small testes, reduced facial hair
  • often STERILE
39
Q

Poly X females

A
  • sex chromosome abnormality due to nondisjunction
  • 3 X chromosomes no Y (XXX)
  • 47 total chromosomes
  • only 1 sex chromosome is functional, other 2 are Barr bodies
  • tall, thin, sometimes normal fertility, normal intelligence

If have more X more severe ex: XXXX OR XXXXX will have cognitive impairment with normal female anatomy

40
Q

Aneupolyploidy

A
  • changes deletion or addition of single chromosomes not based on pair
  • common in humans

3 reasons occurs:

1) loss of chromosome Bc loss of centromere
2) robertsonian translocation
3) nondisjunction

Types

1) nullisomy- loss of both members of homologous pairs (2n-2), lethal
2) monsomy(Turners)- loss of single chromosome (2n-1), if lose single Autosomes lethal
3) trisomy(klinefelters)- gain of a single chromosome (2n+1), lethal
4) tetrasomy- gain of two homologous chromosomes (2n+2)
- two additional chromosomes of same set

41
Q

Polyploidy

A
  • # chromosomes in an entire set change 2n is normal
  • 3n means one chromosome was added to each set, common in plants

Causes:

1) errors in meiosis
2) events at fertilization- dispermy (fertilization of egg with two sperm)
3) errors in mitosis following fertilization

Types:

1) autoploidy- all chromosomes sets (polyploidys) originate from the organisms body itself SAME SPECIES
- due to nondisjunction, no cell division
2) allopolyploidy- polyploidy originated due to hybridization among 2 different organisms
- DIFFERENT SPECIES

42
Q

Principle of segregation vs independent assortment

A

Segregation

  • during the formation of gametes there is a 50/50 chance of getting one of the traits, but can not get both Bc for example it is color can only be one color
  • one trait/characteristic

Independent Assortment
- during formation of gametes TWO alleles with different traits do not influence eachother AT ALL when distributing
- two or more different traits with 50/50 chance of getting either one they DO NOT influence eachother
Ex: height (tall vs short) or color (yellow vs white)
50/50 chance of being tall or short
50/50 chance of being yellow or white

43
Q

Inversion

A
  • chromosome segment breaks off and flips then adds back to the same chromosome

types
1) paracentric inversion- do not include the centromere
- most NONVIABLE (heterozygous)
2) pericentric inversion- include the centromere
- about half of gametes are viable
3) POSITION EFFECT- regulation of genes is sometimes context dependent (can change how it’s going to work, used incorrectly, or unable to see what’s on or off)
Ex: if break in the middle of a gene, gene is null(lost)

44
Q

Deletion

A
  • breaks off part of chromosome and does not reattach
  • if break off centromere lose chromosome completely
  • lethal for homozygous deletions

Heterozygous deletions

1) psuedodominance- loose wild type allele see recessive
- allows recessive alleles on undeleted chromosome to be expressed
2) haploinsufficient- left with wild type allele but not enough to get you wild type phenotype
- some genes have to be present in 2 copies to produce enough gene produce

45
Q

Translocation

A
  • segment of chromosome breaks off and goes onto nonhomologous chromosome
  • nonreciprocal exchange (moves from one to the other without equal exchange)

robertsonian translocation

  • translocation + deletion
  • causes some forms of Down syndrome

Reciprocal translocation
- stitches two random broken chromosomes together Can be in WRONG ORDER

Fundamental genetics (15 decks)

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