genetics Flashcards
Except for the sperm and oocytes (gametes), during development and afterwards, all body cells have _____ total chromosomes
46
the cells in the body other than sperm and egg cells. replicated by mitosis
somatic cells
gametes are produced through mitosis or meiosis
meiosis
Meiosis ___ is a ______ from 2n to n
o The homologous chromosomes are segregated from each other, then two _____ cells are formed, each containing one of the segregates
I. reductive division. haploid
Meiosis ____ consists of decoupling each chromosome’s sister strands (chromatids), then segregating the DNA into two sets (each set having one of each homologue)
o Two haploid cells with replicated sister chromatids go to form four _____ cells with single, unreplicated molecules of DNAs
II. haploid
: How each pair of homologous chromosomes separates has NOTHING to do with each other pair
Independent assortment
: a result of crossing over, it means that even
DNA on the same chromosome may go in different directions (part gets crossed over to the other homologous chromosome)… not all the time but occasionally.
Recombination
Different forms of homologous genes
Alleles
Locations of genes on a chromosomes (different alleles have the same locus on the homologous chromosome)
Locus
both alleles identical
Homozygous
alleles different
Heterozygous
: complete set of genes and alleles
Genotype
observed physical and functional traits (depends on interaction of alleles and environment)
Phenotype
Genetics involves 2 basic things: determining where the alleles for a _____ come from, and then determining the ____ based on that _____
genotype. phenotype. genotype
When the diploid number of chromosomes (2n) is reconstituted in a fertilized ovum, one chromosome in each pair came from the mother, and the other came from the father - these are called
homologous chromosome
Each pair in this genetic sampling of a human cell is a
Homologous pair (look at pic)
Each of the two homologues contains genes that control the ______ (make the ______), though they do so with individual variation characteristic of our species
same traits. same proteins
Alternative forms of a gene that code for the same trait and are at the same location on homologous chromosomes are called
alleles
: gene always expressed, even if heterozygous
Dominant alleles
two copies of gene needed to be expressed,
must be homozygous
Recessive alleles
: heterozygote is an intermediate phenotype
incomplete dominance. ex: white flower x red flower = pink flower
: both phenotypes equally expressed
Codominance. ex: white cow x brown cow = cow with white and brown spots
: more than 2 alleles involved
Multiallelic inheritance. ex: ABO blood type
: multiple genes involved
Polygenic inheritance. ex: hair, eye, and skin color
____ determines sex (presence of Y makes individual male)
Y
Characteristics of what : mostly males with disease (recessive, they only have one X copy), passed to sons by mother, father cannot pass the gene
Sex-linked genes located on sex chromosomes:
is the total collection of genes in a population at any one time. A xxx for a particular trait can be though of as all the cards in a
deck. Each diploid individual gets a 2 allele “hand
A gene pool
is a change in the relative frequencies of
alleles in a gene pool over time
evolution
_____ alone does not lead to evolutionary change in a population
sexual reproduction
The causes of evolution
Mutations (drawing on or erasing the cards)
Genetic drift in small populations(odds, probability v. actual results)
Gene flow between populations (adding/removing cards to/from the deck)
Natural selection (throwing away some hands and not others)
or changes in the nucleotide sequence of DNA, are rare and Random and have little effect on the total gene pool, but they are the Only ultimate source of new alleles
mutation
Key facts on mutation
Direction=
speed=
-Random, can be Totally new
- Minimal (but it can provide a new allele that other mechanisms of microevolution can increase rapidly)
The three main causes of significant change in allele frequencies over time are
– Genetic drift
– Gene flow
– Natural selection
is a change in the gene pool of a population due to chance
– In a small population, chance events may lead to the loss of genetic diversity (10 coin flips v. 10,000 coin flips)
genetic drift
Key facts on Genetic Drift:
direction=
speed=
-Random
- happens a lot faster with small numbers, large populations are usually closer to the actual odds, so they have minimal drift. Can happen suddenly when a population is separated
is the movement of individuals or gametes/spores between populations and can alter allele frequencies in a population
Gene flow
Key facts on Gene flow:
direction=
speed=
- Makes two populations Similar
- depends on how many barriers there are to mating between the two populations
If individuals differ in their probable reproductive success, xxx will alter allele frequencies
natural selection
Key facts on Natural Selection:
Direction=
speed=
- Increase in alleles that give a phenotype making more children on average in the current environment
- depends on how many more offspring
that allele helps you get compared to others
______ is the only mechanism that has a
“direction” that is not random or determined by other populations
Natural selection
Natural selection
- That direction is an increase in alleles that
produce a ______ that on Average
produces more ______ in
the current ______
Phenotype. Offspring. Environment
