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48 terms

IB BIOLOGY GENETICS

genetics
STUDY
PLAY
Gene
a heritable factor that controls a specific characteristic.
Allele
one specific form of a gene, differeing from other alleles by one or a few bases only and occupying the same locus as other alleles of the gene.
Genome
The whole of the genetic information of an organism
gene mutation
a change in the base sequence of a gene.
Base substitution
The smallest possible change is when one base in a gene is replaced by another. An example of this type of mutation is sickle cell anemia
Meiosis
a reduction division of a diploid nucleus to form haploid nuclei.
Homologous chromosomes
chromosomes with the same genes in the same loci but not necessairly the same alleles of those genes.
Random orientation
during prophase I the position of each pair of chromosomes when the spindle attaches is random
Non-disjunction
sometimes chromosomes that should separate and move to opposite poles during meiosis do not separate and instead they both move to the same pole
Karyotyping
chromosomes are arranged in pairs according to their size. Peformed using cells collected by chorionic villus sampling for prenatal diagnosis of chromosome abnormalities.
Prophase I
Chromosome supercoil, homologous chromosomes (bivalents) pair up (synapsis), crossing over occurs resulting in chiasma, centrioles move to opposite poles in animal cells and the nuclear membrane reaks down.
Metaphase I
spindle microtubules attach to centromeres, bivalents line up at the equator.
Anaphase I
the two chromosomes of each bivalent move to opposite poles, thus halving the chromosome number, each chromosome consists of two identical sister chromatids, if crossing over occured they are not identical.
Telophase I
nuclear membrances form, the cel divides to form two haploid cells
Prophase II
Chromosome supercoil, homologous chromosomes (bivalents) pair up (synapsis), crossing over occurs resulting in chiasma, centrioles move to opposite poles in animal cells and the nuclear membrane reaks down. [EXCEPT THERE ARE NO HOMOLOGOUS CHROMOSOMES TO PAIR UP, THUS NO CROSSING OVER]
Metaphase II
spindle microtubules attach to centromeres, bivalents line up at the equator, at the end of the phase the centromeres divide.
Anaphase II
The centromeres spilt, then the two chromatids of each chromosome move to opposite poles
Telophase II
nuclear membrances form, the cel divides to form two haploid cells [EXCEPT TWO CELLS DIVIDE TO FORM FOUR HAPLOID CELLS WHICH WILL DEVELOP INTO GAMETES, THE CHROMATIDS ARE NOW KNOWN AS CHROMOSOMES
synapsis
during crossing over in prophase I, all the chromatids of two homologous chromosomes become tightly paired.
chiasma
where there was crossing over there is an x-shaped structure
recombination
the reassortment of genes or characters into different combinations from those of the parents
Independent assortment
the way one pair of homologous chromosome is segregated (assorted) during formation of gametes (meiosis) is independent of the way any other pair is segregated. (due to random orientation)
autosome
a chromosome that has no genes involved with sex determination. Humans have 22 pairs.
Sex chromosome
a chromosome that has genes involved with sex determination. Humans have 1 pair.
Linkage group
all of the genes that have their loci on the same chromosome.
Polygenic inheritance
inheritance of characteristics controlled by more than one gene.
Genotype
the alleles of an organism
Phenotype
the characteristics of an organism.
Dominant allele
an allele that has the same effect on the phenotype whether it is present in the homozygous or heterozygous state
Recessive alle
an allele that only has an effect on the phenotype when present in the homozygous state
Codominant allele
pairs of alleles that both affect the phenotype when present in a heterozygote
Locus
the particular position on homologous chromosomes of a gene
homozygous
having two identical alleles of a gene
heterozygous
having two different alleles of a gene.
carrier
an individual that has one copy of a recessive allele that causes a genetic disease in individuals that are homozygous for this allele
test cross
testing a suspected heterozygote by crossing it with a known homozygous recessive
multiple alleles
some genes have more than two alleles
ABO blood group
are an example of codominance and multiple alleles
blood type O
ii
blood type A
I^AI^A or I^Ai
blood type B
I^BI^B or I^Bi
blood type AB
I^AI^B
sex linkage
the association of a characteristic with gender, because the gene controlling the characteristic is located on a sex chromosome. (usually the X)
Hemophilia
are produced by a recessive sex allele on the X chromosome. The allele is X^h and the dominant allele is X^H
colorblindness
are produced by a recessive sex allele on the X chromosome. The allele is X^b and the dominant allele is X^B
PCR (polymerase chain reaction)
is used to copy and amplify minute quantities of DNA/
Gel electrophoresis
fragments of DNA move in an electric field and are separated according to their size.
Clone
a group of genetically identical organisms or a group of cells derived from a single parent.