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Biology > Topic 4 - Genetic Information, Variation And Relationships Between Organisms > Flashcards

Topic 4 - Genetic Information, Variation And Relationships Between Organisms Flashcards

1
Q

What do both eukaryotic DNA and Prokaryotic DNA have?

A

Made of DNA nucleotides containing deoxyribose, a phosphate group and a nitrogenous base.
Nucleotides joined together by phosphodiester bonds to make a polymer chain.

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2
Q

Differences between eukaryotic and prokaryotic DNA

A

Eukaryotic DNA - Longer, Linear, Associated with histones
Prokaryotic DNA - Shorter, Circular, Not associated with proteins
In eukaryotic cells, a DNA molecule and the histone proteins form a chromosome.

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3
Q

Characteristics of mitochondria and chloroplasts DNA in eukaryotic DNA

A

Same as Prokaryotic DNA - Shorter, Circular, Not associated with protein

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4
Q

What is Gene?

A

Base sequence of DNA that codes for:
1. Amino acid sequence of a polypeptide
2. A functional RNA

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5
Q

What is a locus?

A

Every gene occupies a particular fixed position on a chromosome

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6
Q

What is the genetic code and its three features?

A

Sequence of three DNA bases (triplet) code for a specific amino acid
- Degenerate
- Universal
- Non-overlapping

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7
Q

What is degenerate (genetic code)?

A

Single amino acid coded for by more than one codon

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8
Q

What is universal (genetic code)?

A

Same triplet of bases codes for same amino acid in all organisms

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9
Q

What is non-overlapping (genetic code)?

A

Each base only part of one triplet of bases that codes for one amino acid. Each codon or triplet of bases is read as a discrete unit.

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10
Q

What are introns?

A

Sections of DNA, don’t code for polypeptides, found in only eukaryotic DNA

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11
Q

What are Exons?

A

Sequence of DNA, codes for amino acids

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12
Q

What’s a codon and the two types?

A

Codon - three bases on mRNA that code for specific amino acid
Start codon
Stop codon

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13
Q

Start codon?

A

Three bases at start of every gene that initiate translation

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14
Q

Stop codon?

A

Three bases at end of every gene that cause ribosomes to detach and therefore stop translation.

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15
Q

Genome?

A

Organisms complete set of genes in a cell

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16
Q

Proteome?

A

Full range of proteins that a cell is able to produce

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17
Q

Do genomes and proteomes change?

A

Genome should never change, but the proteome of the cell constantly changing, depending on which proteins are currently needed.

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18
Q

Messenger RNA -mRNA?

A

Short, single-stranded molecules
Found in cytoplasm and nucleus
Made during transcription - copied from DNA and is therefore complementary to the DNA sequence.

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19
Q

Transfer RNA - tRNA

A

Found in cytoplasm
Amino acids attach to molecules
Sequence of three bases called an anticodon. Complementary to codons on the mRNA molecule.

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20
Q

Pre-mRNA

A

In eukaryotes, after transcription, pre-mRNA is made
mRNA that still contains introns.
Introns spliced out - leaving only exons (coding regions)
In prokaryotes, transcription directly creates mRNA - don’t contain introns in their DNA

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21
Q

Translation

A

Polypeptide chain is created using both the mRNA base sequence and the tRNA

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22
Q

Steps of translation

A
  1. Once modified mRNA has left the nucleus it attaches to ribosome in the cytoplasm
  2. Ribosome attaches to start codon
  3. tRNA molecule with complementary anticodon to start codon aligns opposite the mRNA, held in place by ribosome.
  4. Ribosome move along one codon on mRNA molecule to enable another complementary tRNA to attach to next codon on the mRNA
  5. Two amino acids delivered by tRNA molecules are joined by peptide bond. Catalysed by an enzyme and requires ATP.
  6. Continues until ribosome reaches stop codon at end of mRNA molecule. Doesn’t code for amino acid so ribosome detaches and translation ends.
    Polypeptide chain now created and will enter the Golgi body for folding and modification.
23
Q

Transcription

A

Complementary mRNA or copy of one gene on the DNA is created in the nucleus.
mRNA much shorter than DNA so is able to carry genetic code to ribosome in cytoplasm - enable protein making.

24
Q

Steps of transcription?

A
  1. DNA helix unwinds to expose the bases to act as a template
  2. Only one chain of the DNA acts as a template
  3. Unwinding and unzipping catalysed by DNA helicase
  4. DNA helicase breaks hydrogen bonds between bases
  5. Free mRNA molecules in nucleus align opposite exposed complementary DNA bases
  6. RNA polymerase joins together the RNA nucleotides to create a new RNA polymer chain. One entire gene copied.
    Once copied, mRNA is modified and leaves the nucleus through the nuclear envelope pores.
25
Protein Synthesis?
Proteins created on ribosomes Two main stages: 1. Transcription - one gene on DNA is copied into mRNA 2. Translation - mRNA joins with a ribosome and corresponding tRNA molecules brings the specific amino acid that codon codes for.
26
Gene Mutations
Change in the base sequence of DNA Randomly occur during DNA replication - more likely if exposed to mutagenic agents Could result in either a base being deleted (deletion) or substituted for a different one (substitution)
27
Substitution
Base changed for a different one May have no effect - new codon codes for same amino acid
28
Deletion
Base being removed Results in frameshift - removal of one base changes all subsequent codons
29
Chromosome Mutations
Can arise spontaneously by chromosome non-disjunction during meiosis Changes in structure or number of chromosomes Changes in whole set (polyploidy) Changes in number (aneuploidy)
30
Non-disjunction
When the chromosome or chromatids don’t split equally during anaphase
31
Meiosis
Produces daughter cells that are genetically different from each other. Involves two nuclear divisions and creates four haploid daughter cells from a single haploid parent cell.
32
Variations in Meiosis
Independent segregation of homologous chromosomes Crossing over between homologous chromosomes. Both in meiosis 1 (first division)
33
Independent segregation
In meiosis 1, homologous pairs of chromosomes line up opposite each other at the equator of the cell. Random which side of the equator, chromosomes from each homologous pair lie Pairs separated - each pair end up in daughter cell Creates large number of chromosome combinations in daughter cell.
34
Crossing over
When homologous pairs line up at equator, chromatids can twist around each other Puts tension on chromatids and causes breakage Broken parts recombine with another chromatid which result in new combinations of alleles.
35
Meiosis vs Mitosis
Meiosis - two nuclear divisions, haploid cell (one set of chromosomes), genetic variation Mitosis - one nuclear division, diploid cells (two sets), creates genetically identical cells
36
Genetic Diversity
Number of different alleles of genes in a population Enables natural selection
37
Natural Selection
Leads to evolution in population Results in better adaptations - anatomical, physiology or behavioural
38
Evolution
Change in allele frequency over many generations in a population.
39
Stages of natural selection
1. New alleles for gene created by random mutations 2. If new alleles are advantageous for survival in that environment - more likely to survive and reproduce. 3. Reproduction passes on advantageous allele to next generation. 4. Over many generations, new allele increases in frequency in the population.
40
Types of Selection and aspects
Directional Selection - extremes has the selective advantage, occurs when there’s a change in environment, modal trait changes. Stabilising Selection - modal trait has selective advantage, occurs when there’s no change in environment, modal trait stays the same, standard deviation decreases
41
Species and taxonomy
Two organisms belong to the same species if they are able to produce fertile offspring. Must reproduce to pass on advantageous alleles. Courtship Behaviour essential for successful mating and for species recognition.
42
Courtship Behaviour
Sequence of actions which is unique to each species. How animals identify mates. Mostly performed by males (dance, sounds, feathers) Females observe ritual and decide if they want to mate with the male.
43
Importance of courtship behaviour
Ensures successful reproduction: - enables them to recognise own species and opposite sex - synchronises mating behaviour - indicates sexually mature and in season Ensure survival of offspring: - form a pair bond - strong healthy mate
44
Phylogenetic Classification
Arrange species into groups according to their evolutionary origins and relationships Tells us how closely related species are and how recent their shared common ancestors are.
45
Hierarchy
Smaller groups arranged within larger groups No overlap between groups E.g. classification systems
46
Stages of hierarchy
Domain Kingdom Phylum Class Order Family Genus Species Each group called a taxa
47
Binomial system
Each species universally identified using the binomial (two name) First name = genus, second name = species (e.g. Homo sapiens)
48
Biodiversity
Variety of living organisms within a particular habitat, ecosystem, biome, or earth
49
Species diversity
Number of different species and individuals within each species in a community
50
Genetic diversity
Variety of genes amongst all the individuals in a population of one species.
51
Species Richness
Number of different species in a community
52
Index of diversity
Relationship between number of species in community (species richness) and number of individuals in each species (population) Formula - D=N(N-1)/Totaln(n-1) D=simpsons diversity index N=total number of organisms of all species n=total number of organisms of particular species Larger value=greater species richness
53
Farming techniques
Can reduce biodiversity, so balance must be found between conservation and farming 1. Destruction of hedgerows 2. Selective breeding 3. Monocultures 4. Over-grazing
54
Investigating Diversity
Genetic diversity within or between species can be made by comparing: - frequency of observable characteristics - base sequence of DNA - base sequence of mRNA - amino acid sequence of proteins.

Biology (6 decks)

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