Chapter 8-Sexual Reproduction and Meiosis Flashcards
What is asexual reproduction?
reproduction without a mate.
What is a conjugation?
form of gene transfer in some microorganisms
Asexual reproduction can be successful when?
in a stable environment
When will sexual reproduction be more desired?
in a changing environment
Diploid cells contain…
2 sets of homologous chromosomes (one from each parent)
What do X & Y chromosomes determine in humans?
gender
What does not determine human’s sex?
the 22 homologous pairs of autosomes.
What do homologous chromosomes share?
same size, same banding patterns, same centrosome location
How do homologous chromosomes differ?
they carry different alleles
Gametes are…
haploid cells
What does meiosis do?
halves the genetic materials to produce haploid cells & scrambles alleles
When does fertilization occur?
when gametes fuse (haploid sperm/haploid egg) to form a diploid zygote
What does mitotic cell division produce?
the body’s cells during growth and development
What type of cells undergo meiosis?
specialized germ cells
What cells do not participate in reproduction?
somatic cells
What do diploid germ cells produce?
haploid cells
What do the events of meiosis ensure?
gametes are haploid & genetically variable
What replicates once in meiosis, what divides twice?
DNA, nucleus
What happens before meiosis?
interphase (DNA replication)
Spindle fibers attach to what in meiosis?
kinetochores to move chromosomes
What do homologous pairs do in meiosis 1?
pair up and separate
In what phase in meiosis 1, do chromosomes align?
prophase 1
In what phase in meiosis 1, do chromosomes split?
anaphase 1
What does meiosis 2 produce?
4 haploid cells ( the two products of meiosis II divide, producing 4 cells that each contain half as many chromosomes as a diploid cell)
What does crossing over do?
shuffles alleles (Produces variability when portions of homologous chromosomes switch places)
When does crossing over occur?
prophase 1
When do chromosomes randomly align?
metaphase 1
What is the chance for any orientation of homologous chromosomes at metaphase 1?
all combinations are equally likely
What does fertilization do to the diversity of zygotes?
multiplies it, because any sperm can fertilize any egg cell
How do identical (monozygotic) twins arise?
zygote splits into two embryos (shared placentas)
How do fraternal (dizygotic) twins arise?
develop from separate zygotes (separate placentas)
What division makes identical cell copies and occurs throughout life?
Mitotic division
What division occurs only in specialized cells and only during some parts of the life cycle?
Meiosis
What does polyploidy mean?
extra chromosome sets
Polyploidy cells contain?
1 or more sets of chromosomes
What is a triploid zygote’s possible gametes?
1n, 1n+1, 1n+1, 2n
Nondisjunction results in…
missing or extra chromosomes.
What is nondisjunction?
the failure of chromosomes to separate in meiosis
A sex chromosome abnormality is typically less severe than…
an incorrect number of autosomes
What can chromosomal rearrangement do?
delete or duplicate genes
What does an inversion do?
flips gene order
What happens in a translocation?
two non-homologous exchange parts
Inversions and translocations may do what?
disrupt vital genes
