Biology UNIT 4- Genetic Information, variation, relationships between organisms Flashcards
What are the 4 bases of DNA?
Adenine A
Thymine T
Cytosine C
Guanine G
A=T G=-C
What is the structure of a nucleotide?
Phosphate -ester bond- pentose sugar- glycosidic bond- nitrogenous base.
What are purines and pyrimidines?
Purines- Adenine (A) and guanine(G) [Double ringed structure]
Pyrimidines- Thymine (T) and Cytosine (C) [single ringed structure]
In what way does DNA replicate?
Semi-conservatively
Explain how DNA replicates.
DNA helicase breaks the hydrogen bonds between the DNA helix separating it into 2 strands. Primase puts a a primer on the leading strand (5prime to 3prime) for DNA polymerase to join free nucleotide bases to the complimentary bases on the leading strand. The lagging strand (3prime to 5prime) needs multiple primers for DNA polymerase to work on. This makes fragments which need to be connected by ligase which joins the strands together. This results in 2 daughter strands with half new and half old DNA.
What are the DNA Replication theories?
Conservative- Parent strand acts as template for replication.
Dispersive- Old and New strands are dispersed between each other.
Semi conservative- 2 Daughter strands containing one of the original strands an one new strand.
What is RNA and what are the base pairs?
A single strand made up of nucleotide bases
A-U Uracil replaces thymine.
G-C
What are the different types of RNA?
mRNA- messenger RNA
tRNA- Transfer RNA
rRNA- Ribosomal RNA
What does mRNA do?
- Made in the nucleus during transcription
- Determines the sequence of amino acids for the protein product
- Able to leave the nucleus to associate with ribosomes
- Sequence of nucleotides is the genetic code.
What is Translation?
Complimentary base pairing occurs between the codons of mRNA and anticodons of tRNA.
What is Transcription?
Occurs in nucleus where DNA is used as a template for mRNA
1) RNA polymerase binds to DNA causing it to unzip.
2) DNA & RNA bases link as RNA polymerase joins nucleotides to the RNA molecules (which grow)
3) mRNA reaches termination region and dissociates from the template as transcription is completed.
4) Splicing matures mRNA so the strand can leave the nucleus through nuclear pores.
What is splicing during mRNA transcription?
Introns (non-coding sections) of mRNA stand are removed and the exons (coding sections) are joined together.
What does tRNA do?
- Single polypeptide folded into a clover shape
- One end attached to an amino acid
- Carriers amino acids to the ribosomes in order to make proteins.
- One end has anticodons (complimentary to mRNA codons)
- Carry various amino acids as each acid has a different anticodon sequence.
Why do cells asexually reproduce?
- Growth
- Repair
- Replacement
What are the stages in a cells life?
G1 [Interphase] Synthesis [Interphase] G2 [Interphase] Mitosis Cytokinesis
What are the stages of Interphase and what happens in each stage?
G1- Cellular contents (excluding chromosomes) are replicated, the cells expand, organelles replicate (46 Chromosomes)
Synthesis- DNA replication as each chromosome is duplicated (92)
G2- Final repair/checks
G0- Occasionally a cell may need to die.
What are the stages in mitosis?
Prophase Metaphase Anaphase Telophase Cytokinesis comes after.
What happens to a cell during Prophase?
Mitosis begins cell division
- 46 chromosomes becomes 92
- Chromatids form (copies of DNA)
- Centriols form at each end of the cell
- Spindle fibres attached to centrioles appear
What happens to a cell during Metaphase?
- Chromatids attach to spindle fibres
- Spindle fibres attach at the kineticore
- Chromosomes move to middle of the cell
What happens to a cell during Anaphase?
- Chromatids (pairs of chromosomes) are separated and begin to move to opposite ends of the cell.
- Spindle fibres pull them apart
What happens to a cell during Telophase?
- Two nuclei form
- Chromosomes appear as chromatin (threads)
- Mitosis ends and a nucleus forms
- Spindle fibres and centrioles dissappear
- Cell membranes start to form
What happens to a cell during Cytokinesis?
- Cell membranes move apart to make daughter cells
- Chromosomes re-condense and become smaller
- New daughter cells go back into Interphase.
What is Cancer?
The uncontrolled division of abnormal/mutated cells in a part of the body.
These cells have the ability to migrate to other areas.
What is a tumour?
A large group of abnormal cells piled together in a neoplasm is called tumour. Tumours can develop in any tissue or organ in the body.
What is Binary Fission?
Division into half (Asexual reproduction) of prokaryotes.
Division of bacteria cells.
What are the steps in Binary Fission?
1) DNA strands and plasmids are coppied
2) Move to either end of the cell
3) cells split into two and new cell walls form
4) Cells are not identical completely. DNA / Chromosomes are the same however plasmids may differ from cell to cell.
What is the equation to calculate population time?
b= B x 2^n
b= number of bacteria at end B= number of bacteria at start n= number of generations of division
Out of Eukaryotes, Mitochondria, Chloroplasts and prokaryotes, which have the smallest/ least volume of DNA?
Eukaryotes- most
Prokaryotes- less
Mitochondria/Chloroplasts- least
What proteins surround DNA in Eukaryotes?
Histome proteins
What is the DNA like in Mitochondria, Chloroplasts and prokaryotes?
Circular DNA
In prokaryotes only 1 chromosome and therefore only one version of each gene.
What are 3 properties of DNA?
DNA is universal, as the bases are the same in DNA in all organisms.
DNA is in distinct triplet codes and therefore does not overlap.
DNA is degenerate, more than one codon can code for the same amino acids.
Define Genome
All the DNA of an organism
Define Proteome
The set of expressed proteins in a given type of cell/organism at a given time.
What are the exons and introns?
Introns- non-coding regions of DNA
Exons- coding regions of DNA
What is transcription?
The process where a copy of DNA is made which is called mRNA.
What are the main steps in transcription?
1) DNA in nucleus is unzipped by helicase and the molecule is broken into 2 strands. (antisense 3’-5’ and sense 5’-3’)
2) RNA nucleotides binds to their complementary base pair on the antisense strand and RNA polymerase joins the bases together.
3) the pre mRNA molecule is formed and must be modified in order to leave the nucleus.
How is pre mRNA modified?
- A modified G (Guanine) cap is put on the 5’ end of the transcript.
- A poly-A-tail is attached to the 3’ end. (a long chain of adenine nucleotides)
What is splicing?
A protein called a spliceosome removes the introns and joins together the exons in the mRNA molecule.
The mRNA strand can now leave the nucleus through a nuclear pore.
What is Translation?
The process where mRNA is read and translated into a protein.
Takes place in the cytoplasm
What is a tRNA molecule?
Clover shaped, have specific anticodons for each amino acids.
What are the steps in translation?
1) mRNA leaves the nucleus and enters cytoplasm
2) Ribosomes attaches to the mRNA molecule
3) tRNA’s anticodon complementary base pairs with mRNA’s codon and binds by hydrogen bonds forming.
4) Second tRNA molecule binds to its own complementary base codon.
5) Peptide bonds form between adjacent amino acids
6) first tRNA molecule detaches and leaves its amino acid. This process repeats for other tRNA’s.
7) Ribosome moves along mRNA molecule as tRNA molecules bind and leave (leaving amino acids).
8) When the stop codon is reached the ribosome and tRNA’s detach leaving a polypeptide chain to be folded into a protein.
What is tRNA reactivation and how does it happen?
Once a tRNA molecule has deposited its amino acid it needs to be reactivated (get another amino acid)
Energy form ATP and AMP rejoins an amino acid to the tRNA molecule.
Define Mutation?
Random change to genetic material.
What are the different types of mutation?
Chromosomal- Incorrect segregation of chromosomes
Gene mutations- Change to/rearrangement of bases
What may mutations affect?
Mitotic division
Meiosis/gamete formation
production of proteins
function of proteins.
What is a point/substitution mutation?
Where a base is swapped for another base.
Either:
-silent: forms same protein/coding
-missense: may change protein
-nonsense: base creates a stop codon so only part of the protein is made.
What are indel (insertion/deletion) mutations?
If baes inserted/deleted is not a multiple of 3 then a frameshift occurs.
Almost all codes change causing amino acids to not make proteins. (biggest Problem)
What is the definition of Haploid and Diploid?
Haploid- Half number of chromosomes
Diploid- Number of chromosomes.
Define Chromatid.
1 part of a chromosome pair
Define homologous pair
Set of one maternal/paternal chromosome
Define Allele
Different version of the same gene
Define bivalent
A pair of homologous chromosomes (during meiosis)
Define Cross-over
Exchange of genetic maternal between homologous chromosomes during meiosis in Prophase 1 (chiasmate)
Define independent segregation
Formation of random chromosomes in different cells (in meiosis)
What are the steps in Meiosis?
Interphase Prophase 1 Metaphase 1 Anaphase 1 Telophase 1 Prophase 2 Metaphase 2 Anaphase 2 Telophase 2
What happens during interphase in meiosis?
Same as mitosis,
DNA replicates
What happens in Prophase 1 in meiosis?
Chromosomes condense
homologous pairs line up
Chiasmatas occur where chromatids cross over.
Centrosomes migrate and spindle fibres form.
What happens in Metaphase 1 in meiosis?
Homologous chromosomes line up on equator of the cell.
Random assortment takes place.
What happens in Anaphase 1 in meiosis?
Homologous chromosomes attach to spindle fibres.
Spindle fibres pull chromosomes apart.
What happens in Telophase 1 in meiosis?
Nuclear membranes reform
Chromosomes disperse
Cytokinesis begins
What happens during Prophase 2 in meiosis?
Chromosomes recondense
Centrosomes migrate
Nuclear membranes disperse.
What happens during Metaphase 2 in meiosis?
Chromosomes migrate to the centre.
Spindle fibres form
What happens during Anaphase 2 in meiosis?
Spindle fibres contract
Chromosomes migrate
What happens during Telophase 2 in meiosis?
Nuclear membranes reform
Chromosomes disperse
Cytokinesis completes the cycle.
What is a non-disjunction mutation?
Failure of pairs of homologous chromosomes to separate or failure of sister chromatids to separate during meiosis.
Where one cell may get more than or less than the required number of chromosomes leaving other cells short/too many.
Define genetic diversity
The number of different alleles for genes in a population.
Define genotype
Genetic make up of organisms.
Define Phenotype
The visible characteristics.
Where does genetic diversity come from?
The random assortment and crossing over (chiasmata) of chromosomes during meiosis.
How did darwin come across his theory of natural selection?
Finding slightly different habitats with different types of beaks on finches in the Galapagos islands.
What are the steps in natural selection?
1) Variation in the population due to allele differences
2) More favourable alleles survive adaptations
3) More likely to reproduce
4) Offspring more likely to have the favourable allele
5) increase in favourable allele frequency in the population.
What are the 3 adaptation categories of natural selection?
Anatomical- Structureal features of the organism (e.g long beak)
Physiological- Processes inside of organisms body (e.g tolerance to chemicals)
Behavioural- Acts which an organism does (e.g courtship displays)
What is selection pressure?
An environment factor that confers a greater chance for survival to a reproductive age on some members of the population.
What is stabilising selections?
Selection keeping an allele distribution similar.
often goes against extremes.
What is directional selection?
An extreme allele trait moving the mean and normal distribution towards the extreme trait.
What is disruptive selection?
Selection against the mean population so the 2 extremes of allele population increase.
Define species
A group of organisms that can reproduce to produce fertile offspring.
Give examples of courtship displays
Dancing
Decorating
Colours
Taste/smell
Why do organisms have courtship displays?
Attraction of a mate/opposite sex
stimulate release of gametes
attract same species
How do people name an organism?
Named according to the binomial system of nomenclature first put forward by carl linnaeus.
What are the rules of nomenclature?
Italics if printed
Underlined if written
1st letter of generic name is capital
specific name all lower case
not sure on species then sp.
What is the taxonomic hierarchy?
Kingdom Phylum Class Order Family Genus Species
What is Phylogeny?
Making evolutionary trees.
What do we use to give evidence of classification/evolutionary relationships?
Anatomical evidence Embryological evidence Behavioural evidence Biochemical evidence Immunological evidence
What is anatomical evidence?
Structural similarities (homologies) the more structural similarities the more closely related.
What is Embryological evidence?
Similarities in embryo’s give guidance in classification.
The more similar the embryo’s are the closer they are phylogenetically.
What is behavioural evidence?
Behavioural similarities.
Provide information of phylogenesis.
What is Biochemical evidence?
Comparing the number of amino acids in Cytochrome C
More similar the amino acid the more closely related.
What is immunology evidence?
- Develop antibodies against humans by injecting serum into rabbits.
- Antigens of rabbits make antibodies
- Test against other blood serum samples
- More similar antigens means more precipitate will form and therefore more closely related.
What is Gel Electrophoresis?
Extraction and comparison of DNA samples form multiple species.
Sequences of proteins in DNA strands are compared.
What is DNA Hybridisation?
- DNA strands from two species are mixed
- Complementary bases pair up (via hydrogen bonds)
- More paired up bases means more closer related.
What is convergent evolution?
Organisms that are unrelated.
Have developed similar structures which perform the same job.
How can we use DNA Sequence to determine phylogenies?
- Sequence DNA genes
- Align sequences from different organisms
- Compare similarity between DNA sequences
- Computers form trees of evolution.
How can we test for evolutionary relationships?
- Develop antibodies against humans
- Test antibodies against other animals
- If recognise antigens then they are more closely related to humans.
What is biodiversity?
Number and variety of living organisms in a certain area.
What is genetic diversity?
Variety of genes possessed by individuals in a species.
What is ecosystem diversity?
Range of different habitat within an area.
What is species diversity?
Number of species/ number of each individual species in a community/
What is the equation to measure Biodiversity?
d= N(N-1)/SUM n(n-1)
d= species diversity index N= Total number of organisms of all species n= Total number of organisms of each species SUM= sum of
