GENETICS (incl. meiosis) Flashcards
define chromatin (in context of genetics)
the combination of protein and DNA that make up chromosomes, untangled and loose
define chromatid
one of two identical halves of a chromosome after replication
define chromosome
a threadlike structure of DNA and protein, carrying genetic information in the form of genes.
define diploid vs haploid
A diploid cell has two of each chromosome (a homologous pair) in its nucleus and is notated as 2n. A haploid cell only has one of each chromosome and is notated as n
tetrad/bivalent
a structure formed in zygotene of prophase I, consisting of two homologous chromosomes, each composed of two identical sister chromatids.
chiasmata
X-shaped point of contact between two homologous chromatids where crossing over ocurred
synapsis
the pairing of homologous chromosomes into a tetrad so that crossing over can occur
reduction division
another name for meiosis I, named because it results in cells with half the chromosomes of the original cell
centromere
the constricted region in the centre of a condensed, replicated chromosome, where sister chromatids are attached to each other
kinetochore
the protein complex located in the centromere region of each chromatid to which spindle fibres attach during cell division
telomere
a region of repeating DNA sequences at both ends of each chromosome
list the phases of meiosis including sub-phases of prophase I
PROPHASE I
{
leptotene
zygotene
pachytene
diplotene
diakinesis
}
METAPHASE I
ANAPHASE I
TELOPHASE I
PROPHASE II
METAPHASE II
ANAPHASE II
TELOPHASE II
leptotene
substage of prophase I in which chromosomes begin to condense
zygotene
substage of prophase I in which synapsis occurs, forming a tetrad.
pachytene
substage of prophase I in which chromosomes are fully condensed and crossing over occurs, chromosomes become more distinct and nuclear memebrane disappears
diplotene
substage of prophase I in which the synaptonemal complex dissolves but chiasmata remain, keeping homologous pairs attached
diakinesis
substage of prophase I in which chiasmata separate and spindle fibres form.
crossing over
the exchange of genes between non-sister homologous chromatids, resulting in new combinations of genetic information (recombinant DNA)
gamete
a mature, haploid cell, male or female (sperm or egg) that can fuse with another of the opposite sex to form a zygote
zygote
a fertilized diploid cell resulting from the union of a male and female gamete
nondisjunction and aneuploidy
NONDISJUNCTION is a genome mutation in which either homologous pairs fail to separate (anaphase I) or centromeres fail to separate (anaphase II), resulting in daughter cells with an abnormal number of chromosomes (ANEUPLOIDY)
trisomy
a chromosome present in 3 copies instead of 2 as a result of nondisjunction
monosomy
a chromosome is present in 1 copy instead of 2 as a result of nondisjunction
deletion (chromosome structural mutation)
a segment of a chromosome is lost
duplication (chromosome structural mutation)
a segment of a chromosome is repeated
inversion (chromosome structural mutation)
a segment of a chromosome flips around but remains in place
translocation (chromosome structural mutation)
part of a chromosome changes place with another part of the same chromosome or another chromosome
transition (point mutation)
a single purine base is replaced with another purine base, or a single pyrimidine base is replaced with another pyrimidine base
transversion (point mutation)
a single pyrimidine turns into a purine, or vice versa
insertion (point mutation)
one or more base pairs are inserted into DNA sequence where they shouldn’t be
deletion (point mutation)
one or more base pairs are lost from the sequence
mutagen
a mutation-causing agent like X-rays or cigarette smoke
amniocentesis
a prenatal genetic test that removes amniotic fluid and tests the cells found in it
chorionic villus sampling
prenatal genetic test where cells from placenta are removed and their DNA tested
karyotype
cells are removed from the patient’s body, often blood, and then treated to increase mitotic division. a chemical, colchicine, is added to stop division at metaphase, and then cells are burst open, stained, and photographed to examine the chromosomes in their condensed form
fluorescence in situ hybridization
a genetic test that detects details of specific abnormalities using fluorescent “probe” chemicals that only bond to specific DNA sequences
“gene testing” as a type of genetic test
“analyzes mutations in DNA sequence of a gene” this seems like a stupid general term but it’s all the textbook says. c’est la vie - ay dios mio
biochemical testing (as a type of genetic test)
proteins in the body are tested for abnormalities, which, if present, would be because of genetic abnormalities
allele
one of the two or more forms of a gene (found in same locus) for a specific trait
codominance
the expression of both alleles of a heterozygous pair; neither is dominant over the other
principle of dominance
mendel’s principle stating that when contrasting alleles are crossed, only one will be expressed
gene
a distinct unit of hereditary material found in chromosomes. more specifically, a sequence of nucleotides in DNA in the same locus that codes for a particular protein.
principle of independent assortment
mendel’s principle that different traits are inherited independently of one another. for example, if eye colour and hair colour are on different chromosomes, the inheritance of one does not affect the inheritance of the other
linked genes
genes located on the same chromosome. they are not independently assorted, but rather distributed into gametes together during meiosis, unless crossing over occured
pleiotropy
the condition in which a single gene has more than one phenotypic effect
polygenic inheritance
type of inheritance in which multiple genes affect the same trait
principle of segregation
mendel’s principle that each gamete only has one allele for a particular trait
van Leeuwenhoek’s ideas of inheritance
discovered living sperm and thought he saw a tiny lil man in each sperm cell.
Aristotle’s ideas of inheritance
proposed that egg and sperm (although he didn’t know what sperm cells were) consisted of PANGENES from all parts of the body, which developed into their respective part in the fetus
phenotype
observable traits of an organism determined by its genetic makeup
genotype
the genetic makeup of an organism, can be used in a more narrow sense to refer to specific alleles such as Bb or BB
sex chromosome
humans (and other mammals) have (uuuusually) either XX or XY chromosomes. XX denoted female, XY denotes male. the sex of the zygote is determined by whether the sperm received an X or Y chromosome during its meiosis.
autosome
one of the numbered chromosomes present in homologous pairs in all humans, as opposed to sex chromosomes
XO sex determination
found in some insects, males have only an X chromosome (notated as XO) and females have XX.
ZW sex determination
in birds and some insects, it is the female gamete that determines the sex of the offspring. males have ZZ, and females have ZW
parthenogenesis/haplodiploidy
in hymenoptera (maya that means wasps, ants, and bees - personal attcak is not appreciated but also thank you), males are haploid and grow from an unfertilized egg; this process is called parthenogenesis. females can have male children without needing to mate - this is why captive ant queens can still lay eggs, but not actually grow a colony, if they are unfertilized
homozygous vs heterozygous
homozygous is two of the same allele, heterozygous is two different alleles for the same gene
recombinant DNA/recombination
recombination any process resulting in the formation of a single DNA molecule from multiple others, resulting in a new sequence of alleles. the result is called recombinant DNA and it occurs in crossing over (pachytene)
homologous pair
a pair of chromosomes that have the same genes in the same order, but may have different alleles because one chromosome is paternal and the other is maternal
synaptonemal complex
the complex of proteins that sticks homologous pairs together (synapsis) in zygotene and dissolves in diplotene
