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A level Biology > Unit 4 > Flashcards

Unit 4 Flashcards

1
Q

Define gene

A

A section of dna that contains a code for making a polypeptide and functional rna (the code is a specific sequence of bases)

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2
Q

Define allele

A

Alternate form of a gene at the same locus of a homologous chromosome

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3
Q

Define chromosome

A

Tightly coiled dna in nucleus of eukroyotic cell (23 pairs)

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4
Q

What’s a homologous pair

A

A Chromosome that has identical gene but different alleles

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5
Q

How is dna stored in a eukaryotes

A

-dna is stored in Chromosomes in the nucleus
-dna is liner
Dna is bound and tightly coiled around a protein called his tones
-dna and go stones is called a nucleosome

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6
Q

Dna in prokaryote cell

A

-short circular dna
-no host ones
No nucleus not membrane bound

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7
Q

How is ribosomal dna and mitochondrial dna are similar

A

-short
-circular
-not his tone bound

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8
Q

3 key features of genetic code

A

-degenerate
-universal
-non overlapping

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9
Q

What’s a Start codon

A

First triplet bases at the start of mrna and initiates translation
And codes for an amino acid

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10
Q

What is a stop codon

A

Final three bases of a gene that stop translation and doesn’t code for an amino acid. Marks the end of a polypeptide

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11
Q

What does it mean when we say dna is degenerate

A

There are 20 different amino acids that genetic code has to be able to code
-combination of 3 bases are needed to make 20 amino acids
-(4^n)

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12
Q

Advantage of degenerate

A

Each amino acid is coded by more then one triplet of bases
And this is an advantage because of a point mutation occurs and the base changes it could potentially code for the same amino acid therefore not altering the polypeptide

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13
Q

What does it mean when we say dna is universal

A

same Triplet bases code for the same amino acid in every organism

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14
Q

What is the advantage of dna is being universal

A

Genetic engineering

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15
Q

What does it mean when we say dna is non overlapping

A

Each base in a gene is only part of one triplet of bases that code for an amino acid
-read as discrete units

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16
Q

What is the advantage of non overlapping

A

If a mutation occurs is only effects on triplet therefore only one amino acids in a polypeptide

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17
Q

What is an intron

A

Sections of dna that don’t code for proteins in eukaryotes they needed to be spliced in mrna

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18
Q

Exon

A

Sections of dna that code for amino acids

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19
Q

Genome

A

Complete set of dna in a cell

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20
Q

Proteome

A

Full range of proteins in one cell

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21
Q

Do genomes stay the same

A

Yes genomes don’t Change but proteomes do depending on what protein is needed

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22
Q

What is rna

A

Is a polymer of nucleic acid made from ribose a nitrogenous base (AUTG) and a phosphate group

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23
Q

Characteristics of rna

A

Is much shorter then dna and is single stranded

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24
Q

Function of rna

A

Copy and transfer the genetic code for dna in the nucleus to the ribosomes

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25
3 types of rna
Mrna trna rRNA
26
Characteristics of mrna
Much shorter so it’s able to leave the nucleus. Dna cant leave the nucleus because 1. It’s too big 2. Might be damaged by enzymes It is short lived so it doesn’t get damaged Contains codons which are one triplet base that code for one amino acid
27
What is trna
tRNA is a clover shaped rna held tigether by hydrogen bonds contain anticodons and an amino acid binding site
28
rRNA
Rna and proteins to make ribsoomes
29
Transcription
Last weeks 5 mark answer: A. At a specific gene, an enzyme (DNA helicase) breaks the hydrogen bonds between bases to expose nucleotides B. Free floating RNA nucleotides pair with complementary nucleotides on the DNA template strand: U pairs with A, A pairs with T, C pairs with G and G pairs with C C. RNA polymerase moves along the strand and catalyses the formation of phosphodiester bonds between adjacent RNA nucleotides to form pre mRNA D. mRNA is formed by removal of introns from the pre mRNA and splicing of exons together E. mRNA moves from the nucleus to the cytoplasm through nuclear pores in the nuclear envelope
30
Translation
Translation: A. A ribosome binds to the start codon on the mRNA    B. tRNA molecules with complementary anticodons to the first two codons on the mRNA bind to the mRNA    C. The ribosome catalyses a condensation reaction to form peptide bonds between amino acids attached to adjacent tRNA molecules. This process requires ATP.    D. The ribosome moves along the mRNA molecule to the next codon to catalyse the peptide bond between the next two adjacent amino acids.     E. As this occurs, tRNA molecules are released to be reloaded with an amino acid    F. When the ribosome reaches a stop codon the ribosome, mRNA, last tRNA and complete polypeptide are released
31
What is meiosis
Produces genetically different haploid cells. From one diploid parent cell into 4 haploid cells And includes two nuclear divisions
32
How is variation introduced
1.independent segregation 2. Crossing over 3. One sperm cell and one egg cell
33
What is independent segregation
During meiosis I, when the homologous pairs are lined up opposite from each other the equator of the cell. It is random which side the homologous pair lay. So when the homologous pair are separated it ends up in one daughter cell
34
How do we calculate the number of possibilities of overlapping
2^23
35
What is crossing over
During meiosis I The homologous pairs line up opposite eachother They chromatids can become twisted around eachother this caused tension and the chromatid snaps and breaks off and results in a recombination on the other chromosome and becomes a new combination of alleles
36
Difference between mioeisis and mitosis
Nuclear divisions Identical and variation Haploid and diploid
37
How do you identify meiosis in a life cycle
2n ——> n
38
What else increases variation
2 different gametes. (2^23)^2
39
How does chromosomes mutation occur
Non dysfunction during meiosis
40
What is non dysfunction
When chromoatids do not separate equally or correctly during anaphase
41
Non dysfunction can occur in two forms
1. Polyploidy 2. Aneuploidy
42
What is polyploidy
Changes in a whole set of chromosomes
43
What is anaploydi
Extra chromosomes
44
Define genetic diversity
Number of different alleles of a gene in a pop
45
What is natural selection
Can only occur when there is genetic diversity within a pop
46
What is evolution
Change in allele frequency over generations
47
What does natural selection allow
Better adapted to environment
48
What type of adaptations are there
Anatomical physiological behavioural
49
How does natural selection occur
1. A new allele is formed through a random mutation 2. If the new allele is advantageous then the organism is more likely to survive and increases chances of survival and reproduce 3. The advantageous allele is then past on to the offspring and next generations 4, the allele frequency increases 4.
50
Two types of NS
Directional and stabilising
51
What is DIRECTIONAL NS
One of the extreme traits has been selected and occurs due to change in environment right shifted
52
What is stabilising selection
The modal trait has been selected occurs when there is no change in the environment Standard deviation increases Extremes decrease
53
What is courtship
Behaviour that results in mating, Essential for successful mating to produce fertile offspring and recognising same species
54
What is species
A group of similar organisms that can breed to produce fertile offspring
55
What are courtship rituals
Colourful feathers skin Sequence of movements Fighting Chemical attraction
56
What is the importance of courtsahip
-successful reproduction Helps recognise their from the same species Synchronises mating behaviour( to determine whether they are sexually mature) 2) ensure survival or offspring by producing a pair bond
57
What do similar courtship rituals reveal about a species
That they are more closely related if they have similar courtship rituals
58
What is the binomial system
Identifying species Genus + species
59
Why do different species look similar
-similar environments -similar selective pressures -Produce similar proteins there for similar physical characteristics -have similar alleles that will have selective advantages
60
Classification scale
D K P C O F G S
61
What is heu racy
-small groups a Ranged within larger groups -no overlapping between groups
62
Why do we have a classification system
-understand relationships between species and keep track of change -universal Grouping organisms
63
How do we classify species
-dna -mrna-amino acids -immunology
64
Phylogeny
According to revolutionary origins And what’s more closely related and which species share a common ancestor
65
What term is used to describe populations of different species living in the same habitat?
communities

A level Biology (11 decks)

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