3.1 genes Flashcards
define GENE
a heritable factors
- consisting of a sequence of DNA
- influences a specific characteristic
a gene occupies a ______ position on a __________
specific
chromosome
a specific location on a chromosome is called a?
locus
define alleles
alternative specific forms of the same gene
- code for diff variations of a specific trait
how do alleles differ from one aother
by one or a few bases
homozygous vs heterozygous
2 copies of same allele
vs
2 diff alleles
define genotype
the complete set of alleles for a gene
define phenotype
trait resultant of genotype
define gene mutation
change in NUCLEOTIDE SEQUENCE of a section of DNA coding for specific trait
new alleles are formed via _______
mutation
beneficial mutations are called …
detrimental mutations are called …
neutral mutations are called …
missense mutations
nonsense mutations
silent
what are missense mutations
beneficial mutations –> new variations of a trait
what are nonsense mutations
detrimental mutations –> truncates gene sequence, disrupts normal function
what are silent mutations
neutral mutations with no effect!
what are the 4 types of mutations
- substitutions (diff nucleotide substituted)
- deletions (Remove)
- insertion (add)
- inversion (switch)
how is sickle cell anemia caused 3
- disorder caused by gene mutations (base substitution)
- results from change to 6th codon for the beta chain of haemoglobin
- glutamic acid replaced by valine
what is the change in the 6th amino acid in haemoglobin that causes sickle cell anemia
glutamic acid to valine
what mutation causes sickle cell anemia
base substitution mutation
sickle cell anemia: sequence change in:
DNA
mRNA
polypeptide
GAG –> GTG (template strand: CAC)
GAG –> GUG
Glu –> Val
sickle cell anemia: glutamic acid vs valine ?
glutamic acid: hydrophillic
valine: hydrophobic
sickle cell anemia alters the _____ of haemoglobin
structure
(glutamic acid –> valine)
what does sickle cell anemia result in?
low oxygen levels
sickle cell anemia: so what if valine is hydrophobic? 4
- allows beta subunits to join together
- haemoglobin polymerises into insoluble fibrous strands
- cannot carry oxygen effectively
- changes rbc into sickle shape
why are sickle cells bad? 2
- contain fibrous haemoglobin strands
- may form clots in capillaries = blocked blood supply
