The sexual life cycle (Meiosis) Flashcards
is the scientific study of heredity and
variation
Genetics
is the transmission of traits from one
generation to the next
Heredity
is demonstrated by the differences in
appearance that offspring show from parents
and siblings
Variation
are the units of heredity, and are made
up of segments of DNA
Genes
Genes are passed to the next generation
through reproductive cells called
Gametes
Each gene has a specific location called a ______ on a certain chromosome
Locus
is inherited from each
parent
One set of chromosomes
In _____________ ______________, one parent produces
genetically identical offspring by mitosis
Asexual Reproduction
is a group of genetically identical
individuals from the same parent
Clone
In ______________ ________________, two parents give rise
to offspring that have unique combinations of
genes inherited from the two parents
Sexual Reproduction
is the generation-to-generation
sequence of stages in the reproductive history
of an organism
Life cycle
(any cell other than a
gamete) have 23 pairs of chromosomes
Human Somatic Cells
is an ordered display of the pairs
of chromosomes from a cell
Karyotype
The two chromosomes in each pair are called
Homologous chromosomes, Homologs
The sex chromosomes are called
X and Y
have a homologous pair of X
chromosomes
Human females
have one X and one Y
chromosome
Human males
The 22 pairs of chromosomes that do not
determine sex are called
autosomes
has two sets of
chromosomes
Diploid cell (2n)
For humans, the diploid number is
46
In a cell in which DNA synthesis has occurred,
each chromosome
replicated
A gamete (sperm or egg) contains a single set
of chromosomes, and is
Haploid (n)
For humans, the haploid number is
23
In an unfertilized egg (ovum), the sex
chromosome is
X
In a sperm cell, the sex chromosome may be
either
X or Y
is the union of gametes (the
sperm and the egg)
Fertilization
- The fertilized egg is called a __________ and has
one set of chromosomes from each parent - produces somatic cells by mitosis
and develops into an adult
zygote
At sexual maturity, the ovaries and testes
produce
Haploid gametes
- Gametes are the only types of human cells
produced by _________, instead of mitosis. - results in one set of chromosomes in
each gamete
Meiosis
Meiosis takes place in two sets of cell divisions,
called
meiosis I and meiosis II
Meiosis I results in two haploid daughter cells
with replicated chromosomes; it is called the
Reductional division
Meiosis II results in four haploid daughter cells
with unreplicated chromosomes; it is called the
Equational division
Division in meiosis I occurs in four phases:
Prophase I
Metaphase I
Anaphase I
Telophase I and Cytokinesis
In ________, homologous chromosomes
loosely pair up, aligned gene by gene
Synapsis
In _______ ____, nonsister chromatids
exchange DNA segments
Crossing over
a group of four chromatids
Tetrad
Each tetrad usually has one or more _____________, X-shaped regions where crossing
over occurred
Chiasmata
Crossing over produces __________ ________, which combine genes
inherited from each parent
Recombinant Chromosomes
Division in meiosis II also occurs in four
phases:
Prophase II
Metaphase II
Anaphase II
Telophase II and Cytokinesis
Protein complexes called _________ are
responsible for this cohesion
Cohesins
