Genetic Information
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- Created by: EmiLy1703
- Created on: 28-04-17 21:20
Which cells DNA molecules are short, circular and not wrapped around proteins?
Prokaryotic cells
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How do the DNA molecules in eukaryotic cells look like?
DNA molecules are very long, linear and wrapped around proteins called histones
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What is a chromosome?
DNA molecule and its associated proteins
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Some organelles of eukaryotic cells also contain DNA, such as...
Mitochondria and chloroplasts
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A gene occupies a fixed position called a...
Locus
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A sequence of three DNA bases is called a
Base triplet
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There are ** combinations of bases
64
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- all organisms use the same codons to make the same amino acids
Universal
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- the code is read three bases at a time
Non overlapping
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- an amino acid can be coded for by more than one codon
Degenerate
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***** code for amino acid sequences
Exons
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***** are non coding sequences
Introns
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The complete set of genes in a cell (including those in mitochondria/chloroplasts) is called....
Genome
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The full range of proteins that a cell is able to produce is called....
Proteome
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What unzips DNA?
DNA helicase
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What joins the nucleotides together?
RNA polymerase
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Which method makes mRNA?
Transcription
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How are introns removed from pre-mRNA?
Splicing
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What is on the surface of mRNA?
Codons
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What is on the surface of tRNA?
Anticodons
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Which bases are changed in RNA?
Uracil replace thymine
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What method takes place in the ribosome?
Translation
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True or False: the start codon always makes the same amino acid
True
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Substitutions:
Can be silent if in 3rd base
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What causes frameshift - makes different amino acids?
Deletions/additions
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******** makes a stop codon; ******** makes a different amino acid
Nonsense ; missense
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Non disjunction during meiosis means....
The chromosomes don't separate
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Meiosis produces ******* cells
Haploid
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Homologous chromosomes...
Code for the same characteristics
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Meiosis has...
Two divisions
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Crossing over and independent assortment of chromosomes...
Increase diversity
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Stabilising selection...
Selects the mean in a stable environment
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Directional selection
Selects for an extreme in a changing environment
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Where does transcription occur?
Nucleus
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Give two ways in which the structure of a tRNA molecule differs from that of a DNA molecule
- tRNA single stranded, DNA double stranded - tRNA has uracil base, DNA has thymine - tRNA has ribose, DNA has deoxyribose
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Give one way in which the structure of an mRNA molecule is different from the structure of a tRNA molecule
- doesn't contain hydrogen bonds - base pairs - contains codons - doesn't contain anticodon - straight - not folded - no amino acid binding site - longer
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Explain the difference between pre-mRNA and mRNA
(pre-mRNA) contains introns mRNA contains only exons
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Starting with mRNA, describe how the process of translation leads to production of a polypeptide
-mRNA attaches to ribosome-codon on mRNA binds to anticodon on tRNA-each tRNA brings a specific amino acid-sequence of codons/bases on mRNA determines order of amino acids-formation of peptide bonds/amino acids joined by condensation reactions
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Describe how crossing over occurs during meiosis
Chromosomes in each pair twist around each other. Chromatids break and rejoin to chromatid on sister chromosome
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Describe what happens to chromosomes in meiosis
-chromosomes shorten/thicken/condense-chromosomes associate in homologous pairs-crossing over-join to spindle fibres-at equator/middle of cell-join via centromere-homologous chromosomes move to opposite poles/move apart-pairs of chromatids separated
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Describe what a gene is
A base sequence of DNA that codes for the amino acid sequence of a polypeptide or functional RNA
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Calculate how many bases are required to code for a chain of six consecutive amino acids
18
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Explain how a change in one base along a DNA molecule may result in an enzyme becoming non functional
A different base might code for a different amino acid. The sequence of amino acids in the polypeptide produced will be different. This change to the primary structure of the protein might result in a different shaped tertiary structure. No function
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State the function of the protein found in chromosomes
It fixes the DNA into position
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Distinguish between the structure of mRNA and the structure of tRNA
mRNA is larger, has a greater variety of types and is shaped as a long single helix. tRNA is smaller, has fewer types and is clover-leaf in shape
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State three ways in which the molecular structure of RNA differs from DNA
Any 3 from: - RNA is smaller than DNA - RNA is usually a single strand and DNA a double helix - the sugar in RNA is ribose while the sugar in DNA is deoxyribose - in RNA the base uracil replaces the base thymine found in DNA
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What effect does selective breeding, the Founder effect (a few indviduals form a new colongy) and genetic bottlenecks (numbers reduced e.g. by disease, hunting, catastrophe) have on genetic diversity?
All reduce genetic diversity
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Groups organisms according to their evolutionary history. It shows which species shared a common ancestor
Phylogeny
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A hierarchy is based on shared characteristics ******* groups contain ******* groups with no *******
Large, smaller, overlap
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Don't forget King Phillip Claimed Our Family Gold & Silver
Domain, Kingdon, Phylum, Class, Order, Family, Genus, Species
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What type of behaviour is recognising own species, demonstrating sexual maturity, pair bond, synchronised mating and stimulating release of gametes?
Courtship behaviour
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May be compared through DNA hybridisation (provides more information than amino acid sequence as code is degenerate)
Bases
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Use the fact that similar proteins will bind to the same antibodies e.g. chimp proteins will bind to antibodies which recognise human proteins
Immunological comparisons
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Members of the same species breed to produce...
Fertile offspring
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State which other enzyme is involved in transcription and describe its role
DNA helicase - this acts on a specific region of the DNA molecule to break the hydrogen bonds between the bases, causing the two strands to separate and expose the nucleotide bases in that region
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Explain why splicing of pre-mRNA is necessary
Splicing is necessary because pre-mRNA has nucleotide sequences derived from introns in DNA. These introns are non functional and, if left on, would lead to the production of non functional polypeptides or no polypeptides at all.Splicing removes them
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Name the cell organelle involved in translation
Ribosome
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State two ways in which meiosis leads to an increase in genetic variety
Independent segregation of homologous chromosome and recombination by crossing over
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Explain how a difference in its DNA might lead to an organism having a different appearance and hence the species showing greater genetic diversity
Different DNA - different codes for amino acids - different amino acids - different protein shape - different protein function (e.g. non functional enzyme) - change in a feature determined by that protein - altered appearance-greater genetic diversty
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What is selection?
Selection is the process by which organsisms that are better adapted to their environment survive and breed, while those less well adapted fail to do so
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Distinguish between directional selection and stabilising selection
Directional selection - favours/selects phenotypes at one extreme of a population. Stabilising selection - favours/selects phenotypes around the mean of a population
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Explain what is meant by species diversity
The number of different species and the proportion of each species within a given area/community
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Explain how agriculture has reduced species diversity
The few species possessing desirable qualities are selected for and bred. Other species are excluded, as far as possible, by culling or the use of pesticides. Many individuals of a few species = low species diversity
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Explain why there is a reduction in species diversity when a forest is replaced by grassland for grazing sheep or cattle
Because forest have many habitats with many different species - high species diversity. Grasslands have a single layer, fewer habitats, fewer species and lower species diversity
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Other cards in this set
Card 2
Front
How do the DNA molecules in eukaryotic cells look like?
Back
DNA molecules are very long, linear and wrapped around proteins called histones
Card 3
Front
What is a chromosome?
Back
Card 4
Front
Some organelles of eukaryotic cells also contain DNA, such as...
Back
Card 5
Front
A gene occupies a fixed position called a...
Back
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