Chapter 9 - Genes, Chromosomes and Patterns of Inheritance Flashcards
gamete
egg or sperm cell
germ cells
give rise to gametes and are found in the gonads
somatic cells
cells of the body other than sex cells
die when the organism dies
genotype
the double set of genetic instructions present in an organism
phenotype
visible expression of the genotype in its structural, biochemical and physiological characteristics
chromosome
thread-like structures composed of DNA and protein, and visible in cells during mitosis and meiosis
chromatid
part of a double stranded chromosome
sister chromatids
diploid number in somatic cells
2n
how many chromosomes to humans have
46 chromosomes
23 pairs
haploid number in gametes
n
diploid
refers to organisms or cells having two copies of each specific chromosome
paired set of chromosomes
haploid
having one copy of each specific chromosomes
half
unpaired chromosomes
karyotype
the complete set of chromosome images
autosomes
22 matched pairs of chromosomes in both males and females
non-sex determining chromosomes
heterosome
sex chromosomes
X and Y
homologous chromosomes
have the same gene location at the cnetromere
non-homologous chromsomes
non-matching chromosomes
cell cycle
interphase
M phase
G0 phase
cell cycle interphase
g1 phase (gap 1) s phase (synthesis) g2 phase (gap 2)
G1 phase - interphase
metabolic changes prepare the cell for division
S phase - interphase
DNA replicated
each chromosome now 2 sister chromatids
G2 phase - interphase
double checks
metabolic changes assemble the cytoplasmic materials necessary for mitosis and cytokinesis
M phase cell cycle
mitosis followed by cytokinesis
G0 phase cell cycle
cells are inactive
mitosis
cell division that produces two daughter cells that are identical to the parent cell
PMAT
mitosis - prophase
break down of nuclear membrane
spindle fibres appear
chromosomes condense
mitosis - metaphase
chromosomes align along the centre line
mitosis - anaphase
centromeres divide
sister chromatids move to opposite poles
mitosis - telophase
nuclear membrane reform
chromosomes decondense
spindle fibres disappear
mitosis - cytokinesis
cytoplasm divides
parent cell becomes 2 daughter cells with identical genetic information
meiosis
2 cell divisions that produces gametes
diploid to haploid
produces random combinations
PMATPMAT
meiosis - prophase 1
DNA condenses, forming chromosomes
synapsis
crossing over
synapsis
homologous chromosomes lie side by side
meiosis - metaphase 1
chromosome pairs line up at the equator
independent assortment
meiosis - anaphase 1
disjunction
disjunction
double stranded homologous chromosomes seperate from each other
meiosis - telophase 1 and cytokinesis 1
nuclear membrane reforms
two intermediate haploid cells
meiosis - prophase 2
nuclear membrane breaks down
spindle forms
meiosis - metaphase 2
chromosomes line up at the equator
independent assortment
meiosis - anaphase 2
sister chromatids seperate and become individual chromosomes of the daughter cells
meiosis - telophase 2 and cytokinesis 2
nuclear membrane reform
4 haploid gametes
independent assortment
the process of random segregation and assortment of chromosomes during metaphase 1 of meiosis resulting in the production of genetically unique gametes
crossing over
Prophase 1
exchange of corresponding segments of non-sister chromatids of homologous chromosomes
new combinations of alleles of linked genes
recombinant
gametes that carry new combinations of linked alleles different from those present in the parental organisms
aneuploidy
more or less chromosomes due to non-disjunction in either anaphase 1 or 2
polysomy / polyploidy
reduplication of some of the chromosomes
more than 1 of a particular chromosome
e.g. down syndrome
monosomy
cell has only one copy of a particular chromosome
trisomy
three instances of a particular chromosome
chromosome - duplication
pert of chromosome is duplication
chromosome - deletion
part of chromosome is missing
chromosome - inversion
order of genes is reversed
chromosome - translocation
part of a chromosome or whole chromosome changes location and moves to another homologous chromosome
non-disjunction
failure of normal separation of homologous chromosomes during meiosis or failure of normal separation of the two strands of a double-stranded chromosome during meiosis and mitosis
gene
unit of heredity
made up of a segment of DNA that codes for the production of a particular protein
located on chromosomes
locus
position occupied by a gene
homozygous
person with 2 identical alleles for a particular gene
heterozygous
person with2 different alleles for a particular gene
autosomal genes
genes that are located on an autosome
X-linked genes
refers to genes located of the X chromosome
hemizygous
just single allele for each gene
in males Y
complete dominance
one allele is expressed and completely masks the effect of the other
co-domincance
heterozygous organism shows the expression of both alleles in its phenotype
monohybrid corsses
involves observing the inheritance of a single gene
dihybrid crosses
involves observing the inheritance of 2 genes
multiple alleles
a system in which 3 or more alleles exist for a particular gene
lethal alleles
alleles that fail to code for a functional protein in sufficient amounts
will die prematurely
dominant
refers to a trait that is expressed in the heterozygous condition
requires only a single copy for its phenotypic expression
recessive
refers to a trait that is not expressed but remains hidden in a heterozygous organism
monogenic traits
traits under the control of one gene
show discontinuous variation
discontinuous variation
members of a population can be classified into a few, non-overlapping classes or groups
polygenic traits
traits under the control of two or more genes
show continuous variation
continuous variation
when members of a population cannot be classified into a few distinct groups, they show a variation of phenotypes
genotype + environment =
phenotype
test crosses
involves on parent that is homozygous recessive an is used for identification purposes
linked genes
genes that are located on the same chromosome
autosomal dominant
the gene for the trait unaffected parents will no produce affected
can’t skip a generation
males and females affected equally
X-linked dominant
male will pass to all daughters and no sons
more females than males
must have at least one parent affected
Autosomal recessive
homozygous recessive
can disappear and reappear
unaffected parents can have affected child
X-linked recessive
more males than females
all sons of females effected
all daughters of male
