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
sickle cells are destroyed _____ rapidly
more
= low rbc count
what is the effect of low rbc count due to sickle cells
more rbcs must be made in the bone marrow to replace
- more work = damage bone structure
define genome
the complete set of genetic material in a cell, organism, or organelle
does the genome include non-coding DNA sequences??
yes!!!
human genome is made up of
?? chromosomes
?? base pairs
?? genes
46 chromosomes
around 3 billion base pairs
around 21k genes
what is the Human Genome Project (HGP)
an international cooperative established to sequence the human genome
what did the human genome project show
that humans share the majority of their sequence
what can account for diversity in the human genome
short nucleotide polymorphisms
what were the outcomes of completion of the human geonome project 4
- mapping (number, location, size, sequence set)
- screening: production of specific gene probes = screening of genetic diseases
- medicine: discovered new proteins = better treatments
- ancestry: origins, evo, migratory patterns of man
how are number of genes in a genome predicted
by identifying sequences common to the genes
- difficulties: presence of pseudogenes and transposons + diff approaches to identifying = varied estimations
what databases are used to identify genome stuff
National Center for Biotechnology Information (NCBI)
- Genbank database
- Clustal Omega
