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Biology-Corinna > 17.Inherited Change > Flashcards

17.Inherited Change Flashcards

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1
Q

What is a genotype

A

Describes the alleles the organism has, what its inherited

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2
Q

What’s a phenotype

A

The observable characteristic of organism, it’s the result of interaction between genotype and environment

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3
Q

What’s a gene

A

Length of dna that’s a sequence of nucleotide bases that code for a particular protein/polypeptide

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4
Q

What’s an allele

A

Variation or different form of a gene

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5
Q

What’s a locus

A

Postiiton of a gene on a particular DNA molecule

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6
Q

What’s homozygous and heterozygous

A

When each allele of gene is same

When each allele of gene is different

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7
Q

What is dominant alleles

A

Dominant means the allele that expresses itself in the phenotype

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8
Q

What’s codominant

A

When two alleles contribute to the phenotype

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9
Q

What is monohybrid inheritance

A

Inheritance of single gene

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10
Q

What does a monohybrid cross look at

A

Gametes of female and gametes of male

Eg G G and g g

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11
Q

What is the common ratio when breeding a homozygous dominant and a homozygous recessive

A

Gg, Gg, Gg, Gg

4:0

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12
Q

What’s common ratio when breeding two heterozygous

A

GG, Gg, Gg, gg

3:1

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13
Q

What is the basic law of genetics

A

In diploid organisms, characteristics are determined by alleles that occur in pairs, only one of each pair of alleles can be present in single gamete

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14
Q

What is a dihybrid

A

Inheritance of two characteristics at once

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15
Q

What is the theoretical ratio of a dihybrid between two heterozygous cells

A

9:3:3:1

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16
Q

What is sex linkage

A

A gene carried on the X or Y chromosome

17
Q

Where does the gene for haemophilia lie

A

On X chromosome

Males only get X chromosome from mum

18
Q

What’s autosomal linkage

A

Two or more genes carried on same autosome

19
Q

When do you use chi squared

A

Used to test null hypothesis, suggesting that no significant difference, any difference is due to chance

Sample size larger than 20
Data must be discrete
Only raw counts not percentages
Compare experimental rates with theoretical rates

20
Q

What are multiple alleles and what’s their nature

A

When gene has two or more allelic forms

As only two chromosomes in homologous pair, only 2 out of 3 or more will be present in single organism

21
Q

Explain how to make genetic diagram

Example - Green or yellow pea

A
  • if letters not given, choose single letter for each characteristic (G)
  • higher case is dominant and lower case is recessive G-green g-yellow
  • label parents and state their phenotypes (GG and gg)
  • state gametes produced by each parent (G) (G) (g) (g)
  • use punnet square to show results of random crossing of gametes
  • state phenotype of each genotype (Gg is green)
  • indicate numbers of each genotype
22
Q

Explain how single gene is inherited

A

Mendel peas

  • Green pods repeatedly bred with each other they are pure breeding for green
  • said to be homozygous (two green alleles)
  • if pure breeding green pod crossed with pure breeding yellow pod, first filial will be green pods
  • green is dominant
  • is heterozygous pods crossed together, f2 generation is 3:1 green:yellow
23
Q

What is the law of segregation

A

In diploid organisms characteristics are determined by alleles that occur in pairs, only one of each pair of alleles can be present in single gamete

24
Q

Why are actual results of genetic crosses rarely same as predicted

A
  • Chance determines which gametes fuse with which gamete

- larger samples more likely to show results near theoretical ones

25
Q

Explain dihybrid inheritance

A

Mendel peas

  • round and yellow seeds (both dominant features)
  • wrinkles and green seeds (both recessive features)
  • crossed RRGG with rrgg (R-round or wrinkles, g-yellow or green)
  • gametes are RG and rg
  • offspring is RrGg
  • intercross of offspring gametes ( RG, Rg, rG, rg) gave 9:3:3:1
26
Q

Law of independent assortment

A

Each member of pair of alleles may combine randomly with either of another pair

27
Q

How do you write codominance

A

-Different letter for each characteristic eg fur coat brown, white, black
-written as power (superscript) to letter C
C^W (white fur)

28
Q

If a genetics question gives you a ratio that is not 3:1, or 9:3:3:1 what do you consider?

A

Co dominance

29
Q

How does multiple alleles affect inheritance

A

For blood groups, only two out of three alleles can be present
I^A is dominant or co dominant with I^B and I^o is recessive

30
Q

How is sex determined genetically

A

Female gametes are X and X
Male gametes are X and Y

Inherit one from each parent XY is boy, XX is girl

31
Q

How are sex linked diseases like haemophilia inherited

A
  • X linked genetic disorder that’s caused by defective gene on X chromosomes
  • only shown as a superscript on X
  • H is dominant, for production of protein in blood clotting
  • h is recessive, for haemophilia
  • Males only inherit X from mother, father can pass on X to daughter
32
Q

What is haemophilia

A

When recessive allel with altered sequence of dna nucleotides bases codes for a faulty protein which does not function,
Individual unable to produce functional protein required in blood clotting, leads to slow and persistent bleeding internally
-confined to males as many women die when reach menstruation

33
Q

How many homologous pairs are needed to show all 4 alleles are present

When autosomal linked
When not linked

A

Linked - one homologous pair
Unlinked - two homologous pairs

Genes A and B, if on separate chromosomes 4 possible combos of Ab AB aB ab

Genes A and B in same chromosome, 2 possible combos of AB ab

34
Q

What does not occur if genes are linked

A

Assuming no crossing over, all linked genes remain together during meiosis and pass into gametes together , don’t segregate in accordance with mendels law of independent assortment

35
Q

What is epistasis

A

When allele of one gene affects or masks expression of another in phenotype

36
Q

What’s example of epistasis

A

Mice

  • gene a controls distribution of black pigment in hairs, domintnat A leads to black bands on hair, recessive a leads to uniform black hairs
  • gene b controls colour by determine expression of gene A, dominant B leads to production of melanin, recessive b leads to no pigment of hair therefore white coat
  • if mouse is brown/grey it’s got black banded hair
37
Q

Formula for chi squared

A

Sum of ( (O-E)^2 divided by E)

Biology-Corinna (22 decks)

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