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A A A Level Biology > Patterns of Inheritance 6.1.2 module 6 > Flashcards

Patterns of Inheritance 6.1.2 module 6 Flashcards

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1
Q

what is continuous variation

A

value within a range/quantitative
eg) height, length of stalk

-genetic and environmental factors
-polygenic controlled by a number of genes
no limit on value, 2 extremes

can be shown through standard deviation curve

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2
Q

what is discontinuous variation

A

distinct catagories
-qualitative
-eg) blood group, hair colour, wrinkle or smooth peas
-mongenic/controlled by one or two genes
limited number of phenotypes
no in between catagories

can be shown in bar chart

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3
Q

what is an allele

A

a different form of the same gene

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4
Q

what is a phenotype

A

characteristics displayed by an organism

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5
Q

what is a genotype

A

the alleles an organism has eg) Bb BB bb

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6
Q

what is a dominant allele

A

will always be expressed if present in genotype

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7
Q

what is a recessive allele

A

expressed if two copies are present

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8
Q

what are homozygous alleles

A

same alleles identical alleles for a gene can be dominant or recessive

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9
Q

what are heterozygous alleles

A

different alleles present in the zygote

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10
Q

what is the locus

A

position of a gene on each homologous chromosome

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11
Q

what are homologous chromosomes

A

chromosomes w/ same structure features and patterns of genes

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12
Q

what are Epigenetics

A

(means above genetics) the idea that both nature and nurture affect how an organism looks and acts
eg) rats mums and illnesses such as diabetes
both influenced by genes or lifestyle, look of leaf, obesity

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13
Q

how can genes and environement effect leaf appearance

A

genes code for chlorophyll in normal genome

-environment has determined leaf appearance (physiology causes a change in phenotype)

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14
Q

how can the environment effect the leaf appearance

A

Chlorosis- mineral deficiencies

  • lack of Fe- cofactor for enzymes in chlorphyll production
  • lack of Mg- (Mg is in chlorophyll) chlorophyll can’t be synthesised

also Virus infections which interfere w/ metabolism of chlorphyll production and leaves tissues turn yellow

Etiolation- lack of light- plants turn off chlorphyll production to conserve resources, plants grow abnormally long and spindly due to not enough light.

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15
Q

arguments that obesity is caused by genes example

A
  • ‘ob’ gene codes for secreted protein that may function in cell signalling pathway of adipose tissue so more fat deposits
  • ‘LEP’ gene codes for hormone leptin which is produced by fat cells in proportion to their size eg) bigger cells=more leptin (hormone associated w/ satiety)
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16
Q

arguments that obesity is caused by environment example

A
  • inbalanced calories uptake and use
  • availability of food
  • diet choice
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17
Q

what is a phenotype

A

characteristics displayed by an organism

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18
Q

what is a genotype

A

the alleles an organism has eg. BB bb Bb

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19
Q

what is a dominant allele

A

always expressed if present in genotype

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20
Q

what is a recessive alleles

A

expressed if two copies are present

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21
Q

what does homozygous mean

A

same alleles for gene eg BB or bb either recessive or dominant

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22
Q

what does heteorozygous mean

A

different alleles are present in the zygote

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23
Q

what is the locus

A

position of a gene on each homologous chromosome

24
Q

what are homologous chromosomes

A

chromosomes w/ same structural features and patterns of genes

25
Q

what is epigenetics

A

In biology, epigenetics is the study of heritable phenotype changes that do not involve alterations in the DNA sequence.
idea of ‘nature vs nurture’
example being the rats mum and level of licking being down to nurture. But those that were licked less still had the methyl group attached which switched off the gene for licking. the methyl group is orgionally attached in all rat babies

26
Q

what is the enzyme used in transcription

what are the names of the strands of dna

A

rna polymerase - synthesising strand of mRNA
the coding/ sense strand 5’ to 3’
and the antisense/ template strand 3’ to 5’

27
Q

where does transcription occur

A

nucleus

28
Q

where does translation occur

A

ribosomes in cytoplasm

29
Q

which types of RNA are involved in translation

A

mRNA
tRNA
rRNA

30
Q

what does the tRNA have on it

A

anticodon complementary to codon which syntheisises an amino acid forming a polypeptide chain

look at 10/01/20 if dont understand

31
Q

order of a protein forming?

which enzymes involved

A

DNA replication- DNA polymerase involved forms DNA

Transcription- RNA polymerase involved forms mRNA

Translation- at the ribosome froms polypeptide/protein

32
Q

what is a degenerate code in terms of genetic codes

A

idea that more than one codon can code for amino acid! describes why silent mutations have no effect on phenotype

only 20 amino acids to code for but 64 cobinations of codons (4^3) so some code for same.

33
Q

what is meant by a non-overlapping code

A

Starts with AUG and ends with a stop codon and is read in 5’ to 3’ direction ensuring it is non-overlapping

adjacent codons don’t overlap and no base can take part in formation of more than one codon.

34
Q

what is meant by universal code

A

DNA is universal as all living organisms have genes made up of DNA

35
Q

what is a mutation

A

a change in the base sequence of DNA in cell division and copying which changes the arrangement of genes (structure of chromosome)

36
Q

how is albinism caused

A

enzyme involved in chemical pathway is effected so doesnt have correct active site and can’t catalyse the reaction pathway leading to the formation of melanin. This stops production of enzyme for this and cells cant produce melanin

37
Q

what type of nucleic acid holds together the bases i translation

A

mRNA

38
Q

what effect do stop codons have

A

ensure DNA is non overlapping
they dont code for an amino acid
aka nonsense or termination codons

39
Q

what name would be given to a mutation that changes UUU to UUC

A

substitution

40
Q

what are the 4 types of point mutations

A

substitution ATG&raquo_space; ACG
insertion ATG&raquo_space; ATCG G becomes part of next codon
deletion ATG&raquo_space; AG
inversion ATG&raquo_space; AGT

41
Q

which point mutations cause a frameshift and what does that mean

A

insertion and deletion
the addition or removal of a base alters the reading frame of a gene. It can change every codon after the mutation and can dramatically change the amino acid sequence

42
Q

if the base substitution is silent what does this mean

A

DNA sequence has changed but codon hasnt because the DNA code is degenerate

dont change phenotype and most mutations are this type&raquo_space;>neutral

43
Q

what is a missence base substitution mutation

A

DNA change single nucleotide change results in a codon that codes for a different amino acid (alters

this can have large effects such as sickle cell which is caused by base substitution

44
Q

what is a nonsense base substitution mutation

A

every amino acid coded for after that codon (stop codon) won’t be copied which can cause things like cystic fibrosis if chain stops early

45
Q

what is cystic fibrosis catagorised as

A

severe repiritory problems
inadequate pancreatic function caused by accumulation of sticky mucus

this is due to mutation in CFTR coding gene which means it the final protein can’t allow Cl- ions across cell membranes

46
Q

what kind of point mutation is cystic fibrosis usually caused by

A

deletion

nonsense

47
Q

how does a framshift effect the resulted protein/ polypeptide chain

A

completely inactive/ useless due to reading in translation

48
Q

examples of useful/beneficial mutations

A

> ability to digest lactose-spontaneous mutation but not in many mammals who develop intolerance after suckling
bacterial resistance by natural selection
rat poison resistance
camouflaging shell colours and banding on snails

49
Q

examples of detrimental mutation

A

> sickle cell anemia
albinism
cystic fibrosis
huntingtons

50
Q

how can sickle cell anemia be beneficial?

A

in areas where malaria is present, the parasite/plasmodium can only live in normal red blood cells so anyone heterozygous for sickle cell won’t suffer from malaria.

51
Q

how is sickle cell caused

A

base substitution mutation to mRNA base sequence in transcription and changes the polypeptide is haemoglobin as amino acid changes from Glu to Val

instead of globular protein a more fibrous stranded haemoglobin is formed. Hydrophobic VALine binds to other hydrophobic regions causes clumping and sickle cell shape

52
Q

what are the effects of sickle cell

A

> insoluble haemoglobin formed can’t carry oxygen as effectively so is tired constantly
can from clots in capillaries- blocks blood supply to vital organs
sickle cells destroyed more rapidly than normal red blood cells so low red blood cell count - anemic

53
Q

how can sexual reproduction lead to genetic variation within a species

A

meiosis and the random fusion of gametes at fertilisation

54
Q

what is monogenic inheritance

A

the inheritance of a single gene

55
Q

what is dihybrid inheritance

A

inheritance of two different characteristics caused by two genes which may be located on different pairs of homologous chromosomes
each of these genes can have 2 or more alleles

eg round and yellow peas ect

A A A Level Biology (22 decks)

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