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Biology Component 2 Eduqas > Inheritance > Flashcards

Inheritance Flashcards

1
Q

Define Gene

A

A sequence of DNA occupying a specific locus on a chromosomes coding for a specific polypeptide. Usually consists as 2 or more alleles

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2
Q

Define Allele

A

A different form of the same gene, coding for a specific polypeptide.

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3
Q

What is a Genotype?

A

an organisms genetic makeup and the alleles they possess

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4
Q

What is a Phenotype?

A

represents the characteristics of an organisms which is a product of it’s Genotype and the environment

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5
Q

Define homozygous in terms of alleles

A

When both of the alleles in the gene are the same (e.g. RR or rr)

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6
Q

Define heterozygous in terms of alleles

A

When both of the alleles are different to each other (e.g. Rr)

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7
Q

Define Recessive

A

alleles only expressed in the homozygote (rr)

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8
Q

Define Domiant

A

Alleles always expressed in both heterozygote and homozygote (RR or Rr)

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9
Q

What does mono hybrid inheritance involve?

A

the inheritance of a single gene

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10
Q

Why did Mendel use Pea plants for his experiments

A
  • -> easy to grow
  • -> showed clear phenotype differences
  • ->produce large number of seeds so results were reliable
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11
Q

In Mendel’s first experiment where he crossed purple flowered peas with white flowered peas, how did his F1 generation appear?

A

All the F1 generation were purple

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12
Q

When Mendel self pollinated the F1 generation, how did the F2 generation turn out?

A

3 purple flowers and 1 white flower

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13
Q

What is Mendel’s law of segregation?

A

“the characteristic of an organism is determined by alleles which occur in pairs. Only one pair of the alleles can be present in a single gene”

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14
Q

What is co-dominance?

A

when both alleles involved are dominant so both are expressed equally. (e.g. the ABO blood group where both A B are dominant)

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15
Q

What is incomplete-dominance?

A

both alleles are dominant and are presented in the phenotype as an intermediate rather than both being expressed equally. (e.g. purple and white flowers crossing to make pink flowers)

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16
Q

What is Dihybrid inheritance?

A

the simultaneous inheritance of two unlinked genes (genes on a different chromosome)

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17
Q

what typically is the ratio when looking at dihybrid inheritance?

A

9:3:3:1

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18
Q

what is Autosomal linkage

A

occurs when 2 different genes are found on the same chromosome and can’t segregate interdependently

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19
Q

What is an autosome?

A

any chromosomes other than the sex chromosomes

20
Q

what is Mendel’s law of independent assortment?

A

“each member of an allelic pair may combine randomly with either if another pair”

21
Q

Describe 2 differences between autosomal linkage and sex linkage

A
  • -> sex linkage is usually 1 trait found on the X chromosomes whereas Autosomal linkage is 2 or more traits found on the same autosome
  • -> there are 22 pairs of autosomes which are homolygous where linkage can occur whereas sink linkage only occurs on the 23rd pair which is different in either gender (XX or XY)
22
Q

Define sex linkage

A

when a gene is carried by a sex chromosomes so that a characteristic it encodes is seen predominately in one sex

23
Q

Why do males suffer with sex-linked disorders more than females?

A
  • -> males only receive 1 copy of the X chromosome whereas females have 2
  • -> so, the male only needs one mutant allele to carry the condition and is always expressed as they don’t have a dominant allele on the Y chromosome to overthrow it
  • -> Y chromosome doesn’t carry genes that X does as it is much smaller
24
Q

With the recessive sex linked condition haemophilia:
if h means you Are a sufferer, and H means you are a carrier, what do these mean for females and males:
XH XH
XH Xh
Xh Xh
XH Y
Xh Y

A

XH XH= normal female
XH Xh= female carrier
Xh Xh= Female with haemophilia

XH Y= normal male
Xh Y= male with haemophilia

25
What is Duchenne muscular dystrohpy (DMD) caused by?
X-linked recessive allele and involved gene which codes for dystrophin
26
Define mutation
the change in the amount, arrangement or frequency of the DNA in an organism
27
suggest some characteristics of mutations
- -> can be spontaneous and random occurring anywhere in the genome of diploid organism - -> provides to evolution if it provides an advantageous allele - ->mutation rates can be increased by ionising radiation, X rays and some mutagenic chemicals - -> most common in organism with short life spans - ->occurs mostly during crossing over at prophase I and non-disjuction at anaphase I and II
28
what is addition and subtraction in gene-point mutations?
--> adding or deletion of bases resulting in a frame shift and reading frame moving one place, resulting in non-functioning proteins as the amino acid sequence changes
29
What is substitution in gene-point mutations?
where one base is swapped for another which may result in a change in codon and change in amino acid
30
Describe sickle cell disease as a mutation
- -> involves substitution of adenine and thymine resulting in the change of one amino acid to valine causing red blood cells to deform and block capillaries at low partial pressures of oxygen - -> the alleles for normal and affected haemoglobin are co-dominant so people either have symptoms or severe symptoms - ->those with sickle cell show resistance to malaria so it's a heterozygous advantage
31
why may point-mutations have no effect?
- -> its silent so the base changes but the amino acid which the codon codes for doesn't change - -> may be on non-coding region of intron - ->may be on recessive allele so isn't expressed - -> alters amino acid but doesn't change the functioning of the protein
32
What are chromosome mutations?
changes in the number or structure of a whole chromosome in cells.
33
what is aneuploidy?
when an entire chromosome is added or lost
34
What is it called when one chromosome breaks off and attaches to another?
Translocation
35
How is Down's syndrome caused
when a person inherits all or part of an extra copy of chromosome 21. occurs following non-disjunction of chromosome 21 at anaphase I or II where both copies enter the gamete. once fertilised by a normal gamete, the person now has 3 copies of chromosome 21 (trisomy 21)
36
What the name of mutagen that causes cancer?
carcinogen
37
How is cancer formed?
mutations in protooncogenes produce oncogenes that cause the rate of cell division to increase
38
what is an oncogene?
a protooncogene with a mutation resulting in cancer
39
how does the rate of cell division increase by oncogenes?
- -> mutation causes genes to rearrange and places proto oncogene next to DNA sequence causing excessive mitosis - -> extra copy of proto oncogene results in too much product being made and causing excessive mitosis
40
How do tumour suppressors/ anti oncogenes work?
slows cell division and regulates mitosis | -->But, they can also cause Cell division to increase if the anti-oncogene is mutated and inactivated
41
Define epigenetics
the control of gene expression by modifying DNA or histones without modification of the base sequence
42
How is variation determined?
- -> differences in DNA nucleotide base sequences (alleles) | - -> the enviroment
43
what is genomic imprinting?
when some changes are heritable and asses on if the changes occur in the gametes and whole chromosomes can be inactivated
44
what is DNA methylation is epigentic modification?
addition of methyl of hydroxymethyl to cytosine which reduces the transcription of a gene
45
what is histone modification in epigenetic modification?
- -> occurs post translation - ->addition of acetyl or methyl groups to the amino acid lysine, or the arginine or phosphate groups to serine and threonine - -> increases transcription because RNA polymerase has better access to the DNA as there are looser arrangements of the nucleosomes

Biology Component 2 Eduqas (1 decks)

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