3.1 & 3.2 chromosomes and genes Flashcards
gene
a sequence of DNA that encodes for a certain trait. They are heritable
locus
describes the position of a gene on a certain chromosome
allele
diff forms of a gene
how are new alleles formed?
mutations
allele for sickle cell anemia
HBB found on chromosome 11
how is the sickle cell allele created?
A mutation of one base pair on the 6th codon
which amino acid is substituted in the sickle cell allele?
The 6th amino acid, glutamic acid, is substituted with valine
how many homologous chromosomes need to carry the sickle cell allele for a person to have sickle cell anemia?
both chromosomes
heterozygous advantage
People who carry one normal allele and one sickle cell allele on each homologue will mostly produce normal blood cells and some sickle blood cells. They are healthy. These sickle cells provide an increased resistance against the malaria parasite
gene mutation
a change in the base sequence of DNA
3 types of gene mutations
Beneficial - add new variations of a trait
Detrimental - can disrupt the normal function of that gene
Neutral - have no impact on the normal function of that gene
genome
the totality of genetic information in an organism (or cell)
human genome consists of:
46 chromosomes
~6 billion base pairs
~21,000 genes
draw E. coli (prokaryotic cells
see ipad
how is DNA in prokaryotes structured?
- linear/rod-shaped
- 1 chromosome
- Circular plasmids
- Double-stranded and naked (not associated w/ histone proteins)
how many chromosomes do prokaryotes have?
1 (circular), found in nucleoid
how many bases does a prokaryotic chromosome have?
6,600 to 12,200,000; 1 copy of each gene
plasmid
an independent, small circle of DNA
what do plasmids do for prokaryotic cells?
can contain genes for antibiotic resistance; can be transferred (transformation, transduction, conjugation).
how is DNA in eukaryotes structured?
Eukaryote chromosomes are linear DNA molecules associated with histone proteins
What part of the cell cycle does a cell need to be in in order to produce a karyogram?
metaphase
how are karyotypes constructed from a fetus?
Amniocentesis. This procedure collects a sample of the amniotic fluid that surrounds the unborn baby during pregnancy
Technique for measuring length of DNA molecules by autoradiography (Cairn’s technique)
- Cells grown in medium with radioactive thiamine (T)
- DNA (w/ ra Thiamine) separated out
- Washed w/ a solution containing silver ion (Ag+)
- Plated on film and x-rayed (autoradiograph)
- Measure length of DNA strands
evidence provided by Cairn’s technique
- Chromosome length (uncoiled)
- Bacterial DNA replication forms a replication bubble
- Eukaryotic DNA replication forms a replication fork and is bidirectional
