3 Genes Flashcards
Define Locus
Location of a gene on a chromosome
What is a missense mutation
Benificial mutation - causes a new protein to form creating variation
What is a silent mutation
A neutral mutation which causes no change to the proteins formed
What is a nonsense mutation
A detrimental mutation which leads to no the protein building to stop
What causes sickle cell anemia
A change to the 6th codon of the beta chain of haemoglobin causing a different shaped haemoglobin molecule
DNA - GAG to GTG (non transcribed strand)
What amino acid changes in sickle cell anaemia
Glu to Val
What structure is haemoglobin with sickle cell anaemia
Insoluble Fibrous Strands
What are the possible effects of sickle cells
Clots in the capillaries due to sickle shape
Destroyed rapidly - anaemia due to low red blood cell count
Insoluble haemoglobin is less efficient - lethargy
Define aneuploidy
abnormal number of chromosomes in a haploid set
Define pseudogenes
Non-functional segments of DNA that resemble functional genes
Describe bacterial conjugation
A donor cell replicates it’s plasmid and passes it to a recipient cell via it’s sex pili by creating a conjugation bridge
Describe a nucleosome
8 histone proteins with DNA wrapped around
Describe Chromatosomes
A string of nucleosomes connected by an additional histone protein
Describe a solenoid
A ring of about 6 chromatosomes per turn which condenses to form 30nm fibre
What are homologous pairs?
Name given to the pair of chromosomes with the same loci and structure, one maternal and one paternal
When must homologous pairs be seperated?
Meiosis
Define diploid
Cells with homologous pairs (two sets) of chromosomes (somatic cells)
Define haploid
Cells with only one set of chromosomes (gametes)
Why must gametes be haploid?
So two can fuse to form a diploid zygote
Define Somatic cell
Diploid body cells
Define heterosome
Sex chromosome
Define autosome
Non sex chromosome (other 22 pairs)
Which gene has the male characteristics?
SRY on Y chromosome
What is a karyotype
The number and type of chromosomes in a eukaryote
Define aneuploidies
When an organism has missing or additional chromosomes
Define translocations
Chromosomes break and re-attach to another (chromosomal disorder)
Define karyotyping
Using visual profiles called kariograms to determine chromosomal properties such as gender or identify disorders
Define a non-disjunction event
This refers to the chromosomes failing to separate correctly, resulting in gametes with one extra, or one missing, chromosome
Define Germline cells
Cells that divide into 4 genetically distinct gametes (egg/sperm cells)
What is Mendel’s First Law?
Law of segregation
Each gamete carries only one allele for each gene (they are seperated)
What is Mendel’s Second Law?
Law of Independent Assortment
The segregation of alleles for one gene is separate from any other gene
What is Mendel’s Third Law?
Principle of Dominance
Recessive alleles will be masked by dominant alleles
What zygosity is the sex chromosome in males?
Hemizygous
What are the two possible genotypes for any given gene?
Heterozygous or homozygous
Define phenotype
Physical characteristics
Describe co-dominant alleles
Alleles can both impact on phenotype
Define Mutagens
External factors that increase the rate of mutation (leading to genetic disease)
Define Carcinogens
Mutagens that cause cancer
Give an example of a biological agent which is a carcinogen
HPV virus
What kind of gel is used to separate DNA?
Agarose
What kind of gel is used to separate proteins?
Polyacrylamide
What are proteins treated with before gel electrophoresis to linearize them and uniformize a negative charge?
Anionic detergent
What name is given to the main genetic material in a prokaryote?
Genophore
When does crossing over occur?
Prophase I
What occurs in Meiosis I
Homologous pairs split
What occurs in Meiosis II
Sister chromatids split
Describe the process of crossing over
Non sister chromatids are held together at a chiasma
The homologous chromosomes condense into a bivalent
The bivalent is separated by meiosis creating recombinants
Which factors increase genetic variability?
Crossing over
Random assortment
Random selection
What are the two ways to genetically test foetuses?
Chronic villi sampling
Amniocentesis
Features of chronic villi sampling?
More dangerous
Younger foetus
Features of amniocentesis?
Less dangerous
Older foetus
Name an autosomal recessive disorder
Cystic fibrosis
Name an autosomal dominant disorder
Huntington’s
What does it mean if genes are linked?
They are on the same chromosome
Describe 3 categories of mutagens?
Radiation
Chemical
Biological agents
Why can STRs be used for DNA profiling?
Short tandem repeats are usually unique to each individual
They are cut with restriction enzymes and gel electrophoresis is undergone to compare results
Describe somatic nuclear transfers
The nucleus is removed from an adult skin cell and transferred into an enucleated (nucleus removed) egg
This is then implanted in the womb
Give 4 examples of natural cloning
Binary fission
Budding
Fragmentation
Identical twins
