3.1 Genes Flashcards
a gene is…
a heritable sequence of DNA that determines or influences a trait (physiological, physical, or behavioral)
heritable…
can be passed down from parent to offspring
locus
specific location on a chromosome where each gene is found
(when comparing 2 or more locations, refer to them as loci)
genes have the ____________ both members of a ______________________.
same locus on, chromosome pair
homologous chromosomes have…
the same genes located at the same loci
Alleles are…
alternative forms of a gene that code for the different variations of a specific trait (ex. gene is eye color, alleles are brown and blue)
since alleles are the alternative form of the one gene…
they have very similar gene sequences (only differ by one or a few bases), usually formed by mutation
SNP (single nucleotide polymorphism)
- most common type of genetic variation in people
- when single base pair is replaced with another
- can lead to different alleles/versions of the gene
mutation is…
any unpredictable and permanent change in nucleotide sequence of DNA in an organism- if mutation affects structure or characteristic of a protein, new allele may form
most mutations occur in…
somatic (body cells) and are not passed on from one generation to the next, they are eliminated when the individual dies
only mutations that occur in the formation of …
sperm and egg (gametes) can be inherited
mutagens may…
interact with the DNA and prevent the correct base pairs from bonding during DNA replication
beneficial mutations
change in gene sequence to create new allele/protein that is advantageous to survival and reproduction
harmful mutation
change in the gene sequence to create a new allele/protein that is disadvantageous to survival and reproduction
neutral mutation
change in the gene sequence does not affect survival and reproduction or does not change the allele/protein significantly
missense mutation
change of amino acid (effect could vary)
nonsense mutation
prematurely codes for a STOP codon (shortens protein chain)
silent mutations
has no effect on amino acid sequence (recall: wobble hypothesis)
point mutations
mutations arising from a change in a single nucleotide base
frameshift mutations
mutations (usually insertions or deletions) that cause the reading frame to change (ie. triplet codons are changed)
types of frameshift mutations
- insertion
- deletion
- 3 nucleotide insertion/deletion
sickle cell anemia
occurs due to mutation on chromosome 11, in 6th codon of hemogoblin
what does sickle cell trait do to hemoglobin
leads to production of valine (Hbs) instead of glutamine (Hba)
effect of sickle cell trait on human health
production of abnormal RBCs with faulty hemoglobin gene
- causes Hb molecules to crystallize when oxygen levels in the blood are low
- as a result, RBCs sickle and get stuck in small blood vessels
