Genetics Flashcards
What was exhibited in the F2 generation?
Reappearance of the non-dominant phenotype. Ratio of Dominant : Recessive trait was 1 in 4 (or 3:1)
What did the F1 hybrid generation exhibit?
One of the input phenotypes- dominant trait
What is Mendel’s first law of segregation?
Law of segregation:
Gametes fuse without regard to which alleles they carry
What are digit rid crosses?
When two traits are simultaneously examined
What was Mendel’s second law?
Law of independent assortment: different pairs of alleles segregate independently
What are the three principles of Charles Darwin’s mechanism for evolution?
- There is variation in the expression of traits in a population
- Variant forms of traits can be inherited
- Some variant traits give individuals a better chance of surviving and reproducing-thus continuous RANDOM variations, independent of environment, leads to ‘natural selection’
What is natural selection?
Traits that have a greater probability of surviving to reproduce , thus leading to a population density increase in that trait.
How can be variants occur?
By random mutations
What is paleontology a study of?
The history and development of life on Earth
What did fossil records show?
Extinctions and changes in species
What are homologous chromosomes?
Chromosomes that pair up during meiosis.
Contain the same genes
One comes from each parent
What is the karyotype of human chromosomes?
Visible during mitosis
Humans have 46 chromosomes
What are autosomes?
The other 22 pairs of chromosomes that are homologous
What is mitosis?
When eukaryotic somatic cells divide
What is meiosis?
When germ cells divide. Chromosome number is halved (haploid)
What is interphase?
Most of the cell cycle/longest phase, where the cell prepares for cell division (DNA replication -sister chromatids)
What are the three stages interphase is divided into?
G1: growth after mitosis
S : synthesis of DNA
G2 : growth before mitosis
What is the importance of the G1 and G2 gap phases?
- period of growth-size of cell and protein content increases
- Preparation for next phase- checkpoint that ensures conditions are suitable
What is the G0 phase?
Contains cells that are not actively dividing
What are the five phases of mitosis?
Prophase (Prometaphase) Metaphase Anaphase Telophase
What is cytokinesis?
Division of the cytoplasm
What is the difference between mitosis and meiosis?
Meiosis produces 4 daughter cells which are haploid. Mitosis daughter cells are diploid
What is crossing-over?
When the homologous chromosomes exchange homologous parts
Which phase does crossing over occur?
Prophase
What does independent assortment result in?
Increase in genetic variation within a population
What is linkage?
Two genes on the same chromosome:
Not independently assorted
Segregate together
What is crossing over?
Linked genes should segregate together
Crossing over causes them to separate
Does crossing over reduce genetic linkage?
Yes
What is a histones?
Protein found in chromatid
What percentage of the human genome is genes?
1.5%
What is the percentage genome homology between different people?
~99.9%
What is the percentage genome homology between humans and chimpanzees?
~95%
What does DNA act as a template for in transcription?
mRNA
What is the difference between mRNA and DNA?
mRNA is single-stranded and contains uracil in place of thymine
What is translation?
mRNA into proteins by ribosomes
What does transcription make and where does it take place?
Makes RNA
In the nucleus
What is translation and where does it take place?
Makes proteins
In the cytoplasm
What is the synthesis called in which DNA is replicated?
semi-conservative replication
What are gene promoters and what do they do?
Non-coding, non-transcribed regions
Regulates the expression of genes
What do spliceosomes proteins carry out?
They slice out introns
What are the differences between DNA replication and transcription?
RNA polymerase is used
Only a small portion of DNA is copied (i.e. Genes)
Single-stranded mRNA is made
How many amino acids does one codon make?
One
What does ribosomes do?
Holds mRNA
Links amino acids together
What is the first codon that tRNA binds to?
AUG- methionine
What are the binding sites on tRNA?
Amino acid site
Anticodon
How many tRNA molecules possess anticodons at one end?
64
How many of the 64 tRNA have a specific amino acid?
61
What do the other 3 tRNA molecules have?
Termination signals which stops translation
What is degenerate code?
Different codons specify the same amino far
What is a point mutation?
A single base change
What does substitution mutation result in?
Changes one amino acid
Silent mutation
What does a insertion or deletion result in?
Frameshift Destroys proteins Changes many amino acids Adds a STOP codon Changes shape of protein
What causes damage to DNA?
Mutagens such as : Reactive oxygen species (from metabolism) Radiation (e.g. UV) Environmental chemicals (e.g. Smoking) Viruses
What are the three steps of DNA repair?
- Recognise
- Remove
- Replace
What portion of the population have cystic fibrosis and what portion are carriers?
1 in 2500 have the disease and 1 in 25 are carriers
What type of disorder is cystic fibrosis?
A Monogenic , autosomal recessive disorder
What chromosome is the CF gene located on?
Chromosome 7
What is the chance of offspring being affected if there are two carriers of a autosomal recessive disease?
1/4
What is the name of the protein the CF gene codes for?
Cystic fibrosis transmembrane conductance regulator (CFTR)
What is the most common mutation for CF?
3 base deletion
What are amniocentesis used for ?
Genetic diagnosis
What technique is used to look at specific mutations in genes?
Polymerase Chain Reaction
What is the cause of sickle cell anaemia?
Production of Abnormal haemoglobin (HbS)
When do HbS become sickle-shaped?
When deoxygenated through damage to the cell membrane (fragile and short lived RBCs)
When sickle RBCs become lodged in blood vessels what does this lead to?
Poor downstream oxygen delivery
Ischemia (restricted blood supply)
Infarction (blocked artery)
What can vessel blockage cause?
Episodes of pain
Sores/ulcers
Organ damage (e.g. Spleen , liver)
Stroke (interruption of blood supply to brain)
What disorder is SCA?
Monogenic , autosomal recessive
What mutation caused SCA?
Single mutation in the beta-globin in gene
Do heterozygotes have the disorder ?
Heterozygotes have some sickle cell traits (some sickle cell) but little disease
What is the benefits of SCA and SCT (sickle cell traits)?
Produces some resistance to malaria , as plasmodium parasite causes sickle cells to burst before they replicate
What does the benefits of SCA result in?
High SC population in places where malaria is high
Why can painkillers or intravenous fluid introduction be given for SCA?
To alleviate pain as sickle cells block oxygen flow to tissue/joints
Why may a blood transfusion be give to SCA sufferers?
To increase the number of normal red blood cells in circulation
Why might hydroxyurea an anti-cancer drug be given to SCA sufferers?
Reduces incidence of crises and acute lung syndrome (SCs blocking lung) by stimulating foetal haemoglobin production