Genetics Flashcards
what does DNA stand for?
deoxyribonucleic acid
name the four structures inside DNA
Adenine > Thymine
Guanine > Cytosine
how many chromosomes does a person have?
46 chromosomes (23 pairs)
explain replication
you have a strand of DNA. The enzyme helices cuts it down the middle and from this you can make new stands of DNA.
Primase starts the process - this enzyme makes a smaller piece of RNA (primer) which will be the starting point
Polymerase binds to the primer and makes a new strand.
Enzyme ligase seals the new DNA strand up
explain transcription
instead of Thymine, Adenine pairs with Uriceil
when the gene gets ‘switched on’, RNA polymerase attaches to the strand of the DNA (one strand) it moves along the DNA making a strand out of the free bases in the nucleus. This creates mRNA
explain translation
the mRNA (messenger RNA), moves out of the nucleus and into the cytoplasm
protein factories (ribosomes) bind to the mRNA and reads the code. It provides a chain made up of amino acids.
tRNA molecules carry the amino acids to the ribosomes.
the mRNA is read 3 bases at a time and the tRNA brings the right amino acid
This makes a chain of amino acids which then form a protein
explain mitosis
occurs in somatic (non-reproductive) cells
produces cells with 23 pairs of chromosomes that are identical to the parent cell (diploid)
explain meiosis
occurs in the gonadal tissue to produce gametes
produces daughter cells that have 23 chromosomes each (haploid)
what is an allele?
most of the genome has two versions: one inherited from the mother and one from the father
is different versions of a sequence of DNA
alleles can be dominant (A)
alleles can be recessive (a)
what is homozygous?
if both versions of allele are identical
what is heterozygous?
if the versions of allele are different
what is hemizygous?
if there is only one copy of allele
what is a genotype?
your DNA code for that particular trait
what is a phenotype?
the observational characteristic or trait - the genotype plus the effects of the environment
in inheritance - what is autosomal dominant?
50% chance of passing the condition onto children
males and females equally effected
male to male transmission
in inheritance - what is autosomal recessive?
parents of affected individuals are (usually) unaffected carriers
male and females equally affected
1 in 4 risk
in inheritance - what is x-linked recessive
carrier females have a 50% chance of having an effected male
carrier females and affected males
no male to male transmission
what is diploid?
a cell or a nucleus having 2 sets of chromosomes (pair)
what is diploid?
a cell or a nucleus having a single set of unpaired chromosomes
what are homologous chromosomes?
the cell has two sets of each chromosomes, one pair from the mother and one pair from the farther
what is a karyotype?
number and appearance of chromosomes in the nucleus
what are the first 22 chromosomes called?
autosomes
what is the final pair (23) of the chromosomes called?
the ‘sex-chromosome’
what is telomere?
the structure that seals the chromosomes
what is mutation?
a permanent alteration of the nucleotide sequence of the genome
what is mutagen?
a physical or chemical agent that changes the genetic material
