unit 2 biology
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- Created by: gingerninja46
- Created on: 18-05-15 16:11
what's the function of DNA?
contains all the instructions needed to grow and develop from a fertilised egg to a fully grown adult
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what's the structure of DNA?
double helix formed from 2 separate strands, coiled around each other to form a spiral. strands are polynucleotides
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what's the structure of a nucleotide?
phosphate group, deoxyribose sugar, nucleotide base
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what nucleotide bases pair with what?
A binds with T by means of 2 hydrogen bonds, G binds with C by means of 3 hydrogen bonds
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how does the structure of DNA help it's function?
Double helix makes DNA very stable in cell. DNA doesn't break down/get damaged. DNA molecules are long+coiled up tightly, lots of genetic info fits in nucleus. DNA molecules have paired structure, making it much easier to copy themselves
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how is DNA stored in eukaryotes?
contain linear DNA molecules that exist as chromosomes, each made up of one long molecule of DNA, DNA wound around histones so it can fit into nucleus. DNA coiled tightly to make compact chromosome
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how is DNA stored in prokaryotes?
DNA molecules shorter and circular. DNA not wound around proteins. Condenses to fit into cell by supercoiling.
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what are genes?
sections of DNA found on cells that code for proteins
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what are proteins made from?
amino acids
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what determines the order of amino acids in a protein?
the order of nucelotide bases
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what is each amino acid coded for?
by a triplet in a gene
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what does degenerate mean?
each amino acid has more than 1 codon
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how are genes developed?
DNA sequence determines amino acid sequence. Proteins and enzymes formed.Enzymes control metabolic pathways. Metabolic pathways help determine nature and development.
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what's an allele?
different version of the same gene
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what are homologous pairs?
a pair of matching chromosomes. a human has 23 pairs of chromosomes
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where will alleles coding for the same characteristic be found?
at the same locus on each chromosome in a homologous pair
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what is a mutation?
change in the base sequence of an organisms DNA
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what can mutations do?
produce new alleles of genes or produce a non-functional or completely different protein
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what's meiosis?
DNA unravels+replicates,there are 2 copies of each chromosome (chromatids).DNA condenses to form double armed chromosomes, made from 2 sister chromatids.Chromosomes arrange themselves into homologous pairs.
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what happens during meiosis 1?
homologous pairs separated-halving chromosome number
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what happens during meiosis 2?
pairs of sister chromatids that make up each chromosome separated.4 haploid cells (gametes) that are genetically different from each other are produced.
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how do you create genetic variation of gametes?
crossing over and independent segregation of chromosomes
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what happens during crossing over?
During meiosis 1, homologous pairs of chromosomes come together and pair up. Chromatids twist around each other and bits of chromatids swap over.Chromatids still contain same genes but have different combination of alleles
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what happens during independent segregation?
4 daughter cells formed from meiosis have different combinations of chromosomes. All cells have a combination of chromosomes, half mum, half dad. When gametes are produced, different combinations of maternal and paternal chromosomes go into each cell
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what creates genetic diversity in a species?
difference in alleles
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what factors increase genetic diversity?
mutations in DNA, and gene flow-movement of genes between populations
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what factors decrease genetic diversity?
genetic bottle necks, founder effect and selective breeding
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what are genetic bottle necks?
Large number of organisms in a population die before reproducing. Reduces number of different alleles in gene pool so reduces genetic diversity. Survivors reproduce and larger population created from fewer individuals
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what's the founder effect?
Few organisms from a population start a new colony. Small number of organisms contribute alleles to gene pool, reduced genetic diversity. More inbreeding in new population, increased incidence of genetic disease.
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what's selective breeding?
Humans selecting which domesticated animals or strains of plants to reproduce together to produce useful characteristics. Once organism with desired characteristics has been produced, that organism will continue being bred-reducing genetic diversity.
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evaluate selective breeding
Produces high yielding animals and plants and produces animals and plants with high resistance to disease.Animals and plants can be bred to increase tolerance of poor conditions. Causes health problems and reduces genetic diversity of animals.
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Other cards in this set
Card 2
Front
what's the structure of DNA?
Back
double helix formed from 2 separate strands, coiled around each other to form a spiral. strands are polynucleotides
Card 3
Front
what's the structure of a nucleotide?
Back
Card 4
Front
what nucleotide bases pair with what?
Back
Card 5
Front
how does the structure of DNA help it's function?
Back
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