Higher Biology - Unit 1 - DNA and the genome

name the enzyme that joins fragments together in the lagging strand

ligase

describe how DNA is organised in prokaryotes

circular chromosomes, plasmids

which of the following shows the correct structure of DNA

A

name the substance with which DNA is packaged in eukaryotes

histones

State why the antiparallel nature of the DNA molecule results in \n one of the strands being synthesised in short fragments.

polymerase works from the 5' end to the 3' end

What substances are required for DNA replicatiom

template DNA, enzymes and ATP, nucleotides

explain why primers are necessary for DNA replication

so that DNA polymerase can add nucleotides to the 3' end of the new strand

explain why only the leading strand can be replicated continuously

DNA __polymerase__ adds nucleotides to the 3’ end of the primer/new strand

name protein X

histones

describe one organisational difference between prokaryotic and eukaryotic chromosomal DNA

prokaryotic has circular chromosomes and eukaryotic has linear chromosomes

name molecule x

Amino acid

What is each DNA strand made up of

nucleotides

What are the three parts that make up a nucleotide

Phosphate, Deoxyribose sugar, base

The two strands of a DNA molecule run in opposite directions, this structure is said to be what

Antiparallel

Describe a prokaryotic cell

* no nucleus
* DNA is organised into circular chromosomes and plasmids

Describe a eukaryotic cell

* nucleus
* linear chromosomes

What type of cell is yeast

Eukaryote, however as it also has plasmids

State one location other than the nucleus where DNA is found in eukaryotic cells

Mitochondria, chloroplast and plasmid in yeast

Explain why cells need to carry out DNA replication

So that an exact copy of the genetic material is passed to each new cell

Describe what a polymerase chain reaction technique is

A technique used to create many copies of a fragment of DNA in an __in vintro__ laboratory setting

Name the six requirements for PCR

* Original DNA template
* primer
* nucleotides,
* heat tolerant DNA polymerase,
* thermal cycler,
* buffer solution

What is step one in PCR

Heating to 92-98°C which breaks the hydrogen bonds between the complementary base pairs

What is step two in PCR

Cooling to 50-65°C this allows for the primers to be added

What is step three in PCR

Heating to 70-80°C this allows for the DNA polymerase to be added

How is a cells genotype determined

By the sequence of bases in its gene

\

How is a cells phenotype determined

By the proteins that are synthesised when genes are expressed

What does gene expression involve

The transcription and translation of DNA sequences

Describe transcription in protein synthesis

The synthesis of mRNA from a section of DNA

In the structure of DNA how many strands does it have

Double strands

In the structure of RNA how many strands are there

It is single stranded

In the structure of DNA what type of sugar is there

Deoxyribose

In the structure of RNA what type of sugar is there

Ribose

In the structure of DNA what are the names of the complementary base pairs

Cytosine, guanine, adenine, thymine

In the structure of RNA what are the names of the complementary base pairs

Adenine, Uracil, Guanine, Cytosine

What is the function of mRNA(messenger RNA)

Carries a copy of the genetic code from the nucleus to the ribosome

What is the function of tRNA(transfer RNA)

Each tRNA molecule carries its specific amino acid to the ribosome

Describe the process of cellular differentiation

a cell expresses certain genes to produce proteins characteristics for the type of cell

* (this allows cells to carry out specialised functions)

Define meristems

Meristems are regions of unspecialised cells in plants that can divide (self-renew) and differentiate

Define general stem cells in animals

Stem cells are regions of unspecialised cells in animals that can divide (self-renew) and differentiate

Define embryonic stem cells in animals

Stem cells in the early embryo can differentiate into all the cell types that make up the organism and so are pluripotent

Define tissue stem cells in animals

Stem cells found in tissues throughout the body, involved in growth, repair and renewal of cells found in the tissue and so are multipoint

What does pluripotent mean

**these cells can differentiate into any type of cell**

What does multipotent mean

This means they can **differentiate** **into all** of the **types of cell found in that particular tissue type**

Describe therapeutic uses of stem cells

The repair of damaged or diseased organs and tissues,

examples of therapeutic uses of stem cells

corneal repair and the regeneration of damaged skin

Describe two research uses of stem cells

how disease develop or can be used in drug testing,

Describe the ethical issues surrounding the uses of embryonic stem cells

this involves the destruction of the embryo

Describe the role of non-coding sequences

Regulate transcription by turning genes on/off as regions of DNA activate RNA polymerase to bind to a coding region,

Define mutation

Mutation are random spontaneous changes to an organisms DNA

Describe a substitution mutation

A single nucleotide is replaced with a different nucleotide

Describe an insertion mutation

A single nucleotide is added into a DNA sequence

Describe a deletion mutation

A single nucleotide is removed from the DNA sequence

What is the effect of a substitution mutation

A single amino acid is changed when the protein is being made

What is the effect of an insertion mutation

All amino acids coded for after the mutation are affected as they are moved one base pair up (frameshift mutation)

What is the effect of a deletion mutation

All amino acids coded for after the mutation are affected as they moved one base pair down (frameshift mutation)

What is the effect of a missense mutation

One amino acid is changed for another

What is the effect of a nonsense mutation

A codon that is used to code for an amino acid is changed to a stop codon

Describe a chromosome duplication structure mutation

Genes from one chromosome duplicate and attach to its homologous partner

Describe a chromosome deletion structure mutation

The chromosome breaks in two places

Define evolution

Evolution is the change in organisms **over generations** as a result of genomic variations

Define natural selection

The non-random increase in frequency of DNA sequences that increase survival.

Describe stabilising natural selection

An **average phenotype is selected** for and extremes of the phenotype range are selected against

Describe horizontal gene transfer

Genes are transferred between individuals in the same generation. Prokaryotes and viruses exchange genetic material this way

Define speciation

Speciation is the generation of the new biological species by evolution as a result of isolation, mutation, natural selection

Describe the four step process of speciation

1. An isolation barrier splits a population into sub-populations


2. Mutations take place in each sub-population
3. Natural selection acts on both of the two new sub-populations


4. Speciation has taken place

Define isolation barriers

Isolation barriers **prevent gene flow** between sub-populations during speciation

Describe a geographical barrier

A barrier which physically separates a population by natural features e.g mountain or river

Describe a behavioural barrier

A barrier which separates two populations that are capable of interbreeding

Describe an ecological barrier

A barrier which causes separation by an ecological niche such as pH levels, salinity or breeding locations

Define allopatric speciation

isolated due to geographical barriers

Define sympatric speciation

isolated due to behavioural and ecological barriers

What is the use for bioinformatics

The use of computer and statistical analysis to identify and compare sequence data

What is a molecular clock used for

To estimate when species diverged

By analysing an individuals genome what can be predicted

The individuals likelihood of developing certain diseases

Define pharmacogenetics

This is the study of the genetic variation between individual’s that affect their response to drugs/pharmaceuticals

Describe the use of pharmacogenetics in personal medicine

An individuals personal genome can be used to select the most effective drugs and dosage to treat their disease

Where does transcription take place

The nucleus

Where does translation take place

The ribosome

Describe the process of translation

* gene copied into mRNA strand using RNA polymerase
* primary mRNA transcript is spliced into mature mRNA transcript

Describe the process of transcription

\- mRNA attaches to ribosome \n - tRNA anticodons bind with mRNA codons bringing amino acids together \n - peptide bonds form between amino acids to create a protein

Label points A and B and name the bonds at point C

A: amino acid attachment site B: anticodon C: hydrogen bonds

Which graph is this: directional, stabilising or disruptive?

Disruptive

Which graph is this: directional, stabilising or disruptive?

Directional

Which graph is this: directional, stabilising or disruptive?

Stabilising