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Biology Paper 1/2 > Genetic Information, Variation And Relationship Betweeb Organisms 4 > Flashcards

Genetic Information, Variation And Relationship Betweeb Organisms 4 Flashcards

1
Q

What is loci

A

Position of gene on chromosomes

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2
Q

Why are chromatids identical

A

Genes are at the same locus

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3
Q

What is the genetic code

A

The sent of rules by which information encoded in genetically material is translated into proteins by living cells

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4
Q

Explain the 3 features of the genetic code

A

NON OVERLAPPING: Each base is part of only one Triplet
DEGENERATE CODE: One amino acid can be coded for by more than one Triplet
UNIVERSAL CODE: The same Triplet codes for the same amino acid in all living organisms

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5
Q

What is another name for Triplet

A

Codon

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6
Q

What is beneficial about the genetic code being degenerate

A

If point mutation occurs, even though the Triplet of bases will be different, it may still code for the same amino acid and therefore have no effect

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7
Q

Why is non overlapping in genetic code beneficial

A

If point mutation occurs, it will only affect one codon and therefore one amino acid

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8
Q

What are introns and exrons

A

Introns are non coding base sequence
Exrons are coding base sequence

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9
Q

What happens during splicing

A

Introns are removed, extrons join together to form mRNA

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10
Q

Define genome

A

The complete set of genes in a cell

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11
Q

Define proteome

A

The full range of proteins a cell is able to produce

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12
Q

Why can’t DNA leave the nucleus

A

It is too big and there and there are enzymes in the Cytoplasm which could damage it

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13
Q

What are the two steps in protein synthesis

A

Transcription and Translation

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14
Q

Explain the process of transcription

A

-DNA helicase breaks Hydrogen bonds between bases causing DNA double helix to unwind
-One of the strands of DNA produced acts as a template
-Free nucleotides assemble along the strand of DNA according to the base pairing rule so complementary bases join
-RNA polymerase joins together RNA nucleotides by catalysing formation of phosphodiester bonds
-This makes premRNA
-Introms are spliced out to make RNA

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15
Q

Explain the process of translation

A

-mRNA binds to the ribosome in Cytoplasm
-tRNA moelcules bring specific amino acids to the ribosome
-tRNA’s anticodons bind to complementary codons on the mRNA by forming Hydrogen bonds
-ATP provides energy for the formation of peptide bonds between amino acids
-tRNA is released after amino acids join to form a polypeptide

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16
Q

What is meiosis

A

A type of cell division that produces 4 daughter cells with a haploid chromosome number

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17
Q

Where does meiosis occur

A

Sex cells

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18
Q

Haploid sperm + Haploid egg

A

Diploid zygote

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19
Q

What is an allele

A

Different versions of a gene

20
Q

What is a diploid cell

A

Two complete sets of Chromosomes

21
Q

What is a haploid cell

A

One complete set of Chromosomes

22
Q

Explain all the steps in meoisis

A

PROPHASE 1
-Chromatin condenses and becomes shorter and thicker and this forms two sister chromatids joined together at the centromere
-Homologous Chromosomes pair up to form bivalent
-Crossing over occurs between non sister chromatids of Homologous Chromosomes resulting In exchange of alleles which produces new combination of alleles (happens af chiasma)
METAPHASE 1
Chromosomes line up along equator of cell randomly
ANAPHASE 1
-Spindle fibres contract
-Chromosomes from each pair move to opposite poles
-Centromeres do not divide so each chromosome is still 2 sister chromatids
TELOPHASE 1
-Chromosomes decondense
-Nuclear membrane reforms around 2 groups of Chromosomes
-Cytoplasm divides
-Short period where no action occurs (interkinesis)
PROPHASE 2
-Chromatin condenses
-Nuclear envelope breaks down
-Cell has a haploid number of Chromosomes
METAPHASE 2
-Chromosomes line up along the equator
-Spindle fibres from opposite poles attach fk each sister chromatid
ANAPHASE 2
-Centromere divides and sister chromatids become independent as they move to opposite poles of the cell
TELOPHASE 2
-Chromosomes decondense
-Nuclear membrane reforms
-Cytokinesis occurs
-Each of the 4 new cells produces are genetically different

23
Q

What is haploid and diploid represented by

A

Haploid(n)
Diploid(2n)

24
Q

What is the function of meiosis

A

Sexual reproduction

25
Q

What is the function of mitosis

A

Growth and repair

26
Q

What are 2 types of nondisconjunction

A

Failure of Homologous Chromosomes separating during meiosis I
Failure of sister chromatids sepersting during meiosis II

27
Q

How does nondisconjuction affect number of Chromosomes in gametes

A

Produces gametes with incorrect number of Chromosomes

28
Q

What is a mutation

A

A chnage in the base sequence of DNA

29
Q

What is a substitution mutation

A

Chnage in a single nucleotide base

30
Q

Whar is messence substitution

A

Substitution that results in a single amino acid change

31
Q

What is a nonsense mutation

A

A substitution that results in a stop codon instead of an amino acid usually resulting a non functional protein

32
Q

What two types of mutations cause frameshifts

A

Addition and deletion

33
Q

What are the 3 types of substitution mutations

A

Silent mutations
Missense mutations
Nonsense mutations

34
Q

What is a silent mutation

A

It doesn’t change the amino acid sequence of the polypeptide

35
Q

[6 marks] How does mutation form a non functional enzyme

A

Chnage in base sequence
Change in amino acid sequence
Change in Hydrogen/ionic/disulfide bonds
Chnage in tertiary structure
Chained in shape of active site
Substrate can no longer bind to enzyme as they are not compelemtary so enzyme substrate complex is no longer formed

36
Q

Why are frameshift mutations very harmful

A

All the subsequent triplets are chnaged so chnaged triplets could code for different amino acids resulting in a very different sequence of amino acids resulting in a non functional protein

37
Q

What is translocation in terms of mutations

A

A section of bases on one chromosme detaches and attaches onto a different chromosome
This can cause significant impacts on gene expression and therefore the resulting phenotype

38
Q

What factors cause genetic variation within species

A

-Crossover
-Independent assortment
-mutation
-gametes fusing randomly during fertilisation

39
Q

What is genetic diversitiy/variation

A

Sym of different alleles of genes in a population

40
Q

What needs to be present for natural selection to occur

A

Genetic diversity

41
Q

Explain the process of natural selection

A

-There is genetic variation in individuals of the same species due to random mutations
-Some alleles give an advantage and individuals with the advantageous alleles are more likely to survive and reproduce
-This passes on the advantageous alleles to offspring
-This increases allele frequency of the advantageous alleles

42
Q

What are two types of natural selection

A

Stabilising selection
Directional selection

43
Q

Explain directional selection

A

-Change in environment
-One of the extremes has the selective advantage
-Individuals with alleles for characteristics of an exteme type are more likely to survive and reproduce

44
Q

Explain stabilising selection

A

-No change in the environment
-Favours alleles around the middle
-Individuals with alleles for charectersjtics towards the middle of the range are more likely to survive and reproduce

45
Q

Natural selection Samsung notes

A

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Biology Paper 1/2 (4 decks)

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