Chapter 13 Flashcards
define heredity
heredity is the transmission of traits from one generation from the next
defne variation
variation is demonstrated by the differences in appearance that offspring show from parents and siblings
define genetics
genetics is the scientific study of heredity and variation
what is inherited from parents?
genes are inherited from parents
what are genes?
genes are the units of heredity and are made up of segments of DNA
what are gametes?
reproductive cells (sperm and eggs)
what is a locus?
a gene’s specific position along a chromosome
what happens in asexual reproduction?
a single individual passes all of its genes to its offspring without the fusion of gametes
what is a clone?
a clone is a group of genetically identical individuals from the same parent
what happens in sexual reproduction?
two parents give rise to offspring that have unique combinations of genes inherited from two parents
how many chromosomes are in somatic cells?
46 in total; 23 pairs
what is a karyotype?
a karyotype is an ordered display of the pairs of chromosomes from a cell
mitosis vs meiosis and amount of end chromosomes
in mitosis if you start with 46 chromosomes and you copy them,
- you start with and end with the same number of chromosomes
in meiosis, you use less chromosomes
**only diploid cells undergo miosis
haploid: have one complete set
what are female chromosomes?
they have a homologous pair of X chromosomes
what are male chromosomes?
males have one X and one Y chromosome
what are autosomes?
the remaining 22 pairs of chromosomes
what happens in metaphase one?
pairs of homologs line up at the metaphase plate, with one chromosome facing each pole
what happens in anaphase one?
separating homologous chromosomes, one of each moves to opposite poles, sister chromatids are attached at centromere and move as one unit, which reduces the number of chromosomes
when does crossing over take place and what happens?
in prophase 1: each chromosome pairs with its homolog and crossing over occurs
what happens in telophase one?
each half of the cell has a haploid set of chromosomes, each still has 2 sister chromatids, cytokinesis occurs simultaneously forming two haploid daughter cells
what happens at the end of meiosis 2?
you end up with 4 daughter cells (gametes) that are all haploids
if you have 6 sets, how many sets would gametes have?
3; it reduces in half
what is a diploid cell?
a diploid cell has two sets of chromosomes (2n)
- for humans the diploid number is 46 (2n=46)
what are sister chromatids?
sister chromatids are when each replicated chromosome consists of two identical sister chromatids the > < parts in the
>< chromosome are sisters
if a cell which was 2n=6 (diploid with 6 chromosomes) underwent meisois, what would be produced?
3 haploid daughter cells
what is haploid?
a gamete (sperm or egg) contains a single set of chromosomes and is haploid
what is a life cycle?
a life cycle is the generation to generation sequence of stages in the reproductive history of an organism
what are gametes produced by in comparison to other human cells?
gametes are produced by meiosis, everything else by mitosis
how many sets of chromosomes are in each gamete as a result of meiosis?
one set of chromosomes in each gamete
how does mitosis interact with gametes?
gametes fuse to form a diploid zygote that divides by mitosis to develop into a multicellular organism
which cells can undergo meiosis?
only diploid cells
which cells can undergo mitosis?
either haploid or diploid cells can divide by mitosis
what are sites of crossover called?
chiasmata
what is the main purpose of meiosis one?
to separate homologous chromosomes
what happens during crossing over?
occurring in prophase I, sister chromatids held together by cohesins and nonsister chromatids are broken at corresponding positions, dna breaks are repaired, joining DNA from one nonsister chromatid to corresponding segement of another
what does mitosis produce?
cells genetically identical to parent cell
what does meiosis produce?
cells that differ genetically from each other and from parent cell
where does synapsis of homologous chromosomes occur?
only in meiosis
how many division are apart of mitosis?
one: pmat
how many divisions are apart of meiosis?
2; each with pmat
what are events unique to meiosis?
- synapsis and crossing over in prophase I: homologous chromosomes physically connect and exchange genetic info
- homologous pairs lining up at the metaphase plate in metaphase I
- separation of homologs during anaphase I
what happens in mitosis relating to cohesions?
cohesins are cleaved at the end of metaphase
what happens in meiosis relating to cohesions?
cohesins are cleaved along the chromosome arms in anaphas 1 (separation of homologs)
which mechanisms contribute to genetic variation?
- independent assortment of chromosomes
- crossing over
- random fertilization
what does crossing over produce?
recombinant chromosomes: which combine DNA inherited from each parent
