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
sickle cell relation to malaria
malaria invades RBCs and causes them to lyse
- people with sickle cell trait are resistant to malaria
- sickle cell anemia is more prevalent in areas where malaria is endemic (found)
genome:
whole genetic information of an organism contained in the DNA
genome in plants:
all DNA in chromosomes, nucleus, mitochondrion, chloroplast
genome in prokaryotes:
much smaller, is the DNA in circular chromosome and in plasmids
genome in humans:
consists of 46 nucleic acids that form the chromosomes in the nucleus and DNA in mitochondrion
chromosomes in humans:
chromosome pairs 1-22 are autosomes
23rd pair are sex chromosomes (XX is female, XY is male)
karyogram:
visual display of all chromosomes in a cell
human genome project (HGP)
aimed to find the complete sequence of DNA bases in human genome
finding of the HGP
- humans have 23,000 genes (less than expected)
- the majority of genome is not expressed, these are found to regulate gene expression
- many sections of DNA have regulatory functions
- genome sequence was from one individual so there might be minor differences between individuals
why bother with HGP
could help with gene mapping, screening, medicine, ancestry
genes of humans vs other organisms
bacteria< chicken< human < water flea < rice
techniques for gene sequencing
- gel electrophoresis separates samples of DNA and creates bands that can be used for deduction
- coloured flurescent markers mark DNA copies and uses optical detector to deduce base sequence based on fluorescence colours
