Topic 4 - Genetic information, variation and relationships between organisms Flashcards
What is the structure of a chromosome
Two sister chromatids connected by a centromere
What is DNA associated with to form a chromosome
Histone proteins
What feature of chromosomes means they can store lots of genetic information
Coiled and loops
Define homologous chromsomes
A part of chromosomes, one maternal and one paternal, with the same loci at the same positions
Define haploid
Cells containing one dpi of each chromosome (only 23 chromosomes)
Define diploid
Cells containing both sets of chromosomes (46 chromosomes)
Gene
A section of DNA coding for a particular polypeptide or functional RNA
Allele
An alternative form of a gene
Locus
The position of the gene on the chromosome
What are 2 names for 3 nitrogenous bases in a gene
Triplet or codon
What does a triplet code for
An amino acid
How many combinations of triplets can there be
64
How many amino acids is there
20
What does the phrase non-overlapping mean
Each base in the sequence is only read once
What des the phrase degenerate mean
Each amino acid is coded by more than one triplet
What does the phrase universal mean
Each triplet codes for the same amino acid in all organisms
What does the fact that triplet codes are universal lead to
indirect evidence for evolution
What is the genome
All the genetic information in a cell or organism
What is the proteome
All the proteins that a cell or organism can produce
What is protein synthesis
The production of polypeptides from information stored in a cells DNA
What are the 3 types of RNA
mRNA, tRNA, rRNA
What does mRNA stand for
Messenger RNA
What does tRNA stand for
Transfer RNA
What process is mRNA involved in
Transcription
What process is tRNA involved in
Translation
What happens in transcription
A copy of the gene is made into mRNA
What happens in translation
mRNA binds to a ribosome and the genetic code is converted into a sequence of amino acids to make a protein
What are some features of mRNA
-single stranded helical shape
-sequences of codons code for an amino acid
-moves into the ribosome acts as a template
-The sequence and length is determined by DNA
What are features of tRNA
-single stranded clover shape due to hydrogen bonds between nitrogenous bases
-Transports amino acids to the ribosome to form polypeptides
-Contains an anti codon
-Contains a binding site for the protein
Which type of RNA contains an anticodon
tRNA
Which type of RNA contains an single stranded helical shape
mRNA
Which type of RNA contains a clover like shape
tRNA
Which type of RNA acts as a template for protein synthesis
mRNA
Where does transcription take place in eukaryotic cells
nucleus
Where does transcription take place in prokaryotic cells
cytoplasm
What enzyme is used in transcription
RNA polymerase
What does RNA polymerase do in the first step of transcription
The hydrogen bonds between nitrogenous bases are broken to reveal the template strand
What happens to the template strand
free RNA nucleotides binds and RNA polymerase forms phosphodiester bonds to form mRNA transcript
what stops the RNA poymerase
a terminator sequence
What happens after the terminator sequence
DNA is reformed and pre mRNA is formed
How does pre mRNA turn into mature mRNA
splicing
What two types of regions are their in pre mRNA
exons and introns
what is an exon
an expressive region (coding)
What is an intron
An interrupting region (non-coding)
What type of regions does mature mRNA contain
exons only
Where does the mature mRNA leave through
nuclear pores
What does translation produce
a poly peptide
what are ribosomes made from
proteins and rRNA
what does the mRNA bond to at the start of translation
A ribosome
what is at the start of every mRNA
a universal start codon
What does tRNA carry
A specific amino acid
how does the tRNA bind to the mRNA
Through complementary base pairing between the codon and anticodon
what type of bond are formed between the amino acids
peptide bond
What type of reaction forms polypeptides
condensation
what stops the formation of the poly peptide chain
A stop codon
What is required for the condensation reaction to take place and form a poly peptide
ATP
how many bases code for an amino acid
3 bases (a codon)
What are the two types of mutations
Gene and Chromosome
What are gene mutations
When a nucleotide is substituted in or deleted from the gene
What are chromosomes
Change in the number or structure of chromosomes
What can substitution mutations lead to and why is this less harmful,
Silent mutations since the genetic code is degenerate a change will not necessarily lead to a change I amino acid
What do deletion mutations lead to and why is this more harmful
Frame shift meaning a complete change in the codons so different Amino acids so diff 1 structure so diff 3 structure meaning different function
what are the causes of gene mutations
ionising radiation, errors in DNA replication, mutagenics such as chemicals and viruses
what are the causes of chromosome mutations
non disjunction during meosis
What is a diploid cell
Has two of each chromosome
What is a haploid cell
Has one of each chromosome
Fertilisation
When the nucleus of the male and female gamete fuse
Zygote
A fertilised egg
First step in meiosis
There are homologous pairs of chromosomes
Homologous pair
One maternal one paternal which the same genes in the same loci
second step in meiosis
Chromosomes replicate forming sister chromatids held together by a centromere
third step in meiosis
homologous pairs line up and crossing over occurs
crossing over
When a chromatid breaks and rejoins with its homologous pair
fourth step in meiosis
homologous pairs randomly separate into two daughter cells (independent segregation)
Independant segregation
random combinations of chromosomes
5 step in meiosis
Sister chromatids spilt and cell divides
Final step of meiosis
4 genetically different haploid cells
What is the cause of variation in both sexual and asexual reproduction
Mutation
What are the causes of variation in only sexual reproduction
Crossings over, independent segregation and random fertilisation
What is genetic diversity
The total number of different alleles in a population
What is a gene pool
The total number of alleles in a population
What can genetic diversity be increased by
Mutations and migration (intro of new alleles)
How do you work out the number of combinations
2 to the power of n where n is the number of chromosomes
What do advantages alleles increased over time
greater chance of survival and reproduction as alleles are passed on to offspring so allele frequency in the gene pool increases
what is selection
The process by which better adapted organisms will survive to reproduce and pass on genes
What are the three types of selection
directional, stabilising and (distributive)
What is directional selection
When an extreme phenotype is selected for over other types.
What is an example of directional selection
Antibiotic resistance, giraffe necks
When does directional selection occur
When there is a mutation giving a selection advantage and when there is a sudden change in environmental conditions
What is stabilising selection
When the mean phenotype is selected for over extreme phenotypes.
When does stabilising selection occur
When the environment is more stable
What are examples of stabilising selection
Bird number of offspring
Birth weight
What is taxonomy
The theory and practice of biological classification
What are the 8 components of the classification hierarchy
Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species (Kids playing chicken on freeways go splat)
How do we know it is a classification hierarchy
Each organism is in one group and there is no overlaps and there are smaller groups within larger groups
What is each tier of the hierarchy known as
Taxa
What is binomial meaning
Two names
What language is the binomial system based on
Latin
What are the rules for the binomial system
The generic name (genus) starts with a capital and the specific name (species) starts with lowercase. The whole name is in italics
Why is the binomial system important
So scientists know they are referring to the same organisms
What is phylogeny
the evolutionary relationship between organisms and their common ancestors
Who’s theory is it that all organisms evolved from a common ancestor
Charles Darwin
What is courtship behaviour
Signals organisms use to recognise individuals of the same species and if they are prepared to mate
Why is courtship behaviour important
- individuals of the same species are recognises
- Identifying mates capable of breeding
- Form a pair bond (to raise offspring)
- Synchronise mating ( max probability of sucessful fertilisation)
- Becoming sexually mature
