Bio lesson 1.2 key terms Flashcards
(29 cards)
What is meiosis
To produce haploid (n) gametic cells
that contain different genetic information for sexual reproduction (fertilization)
Located in the Gonads
what is this purpose and stages of meiosis I
Purpose: Reduce the chromosome # by one half. Separation of homologous chromosomes.
Prophase 1, Metaphase 1, Anaphase 1, Telophase 1
what is the purpose and stages of meiosis II
Purpose: Separation of sister chromatids (similar to mitosis)
Prophase 2, Metaphase 2, Anaphase 2, Telophase 2
Before meiosis I there is Interphase I , if so what are the steps
Step 1: G1 Phase (Growth Stage/Preparation for Mitosis)
Stage 2: S Phase (Chromosome
Duplication/Preparation for Mitosis. Two identical sister chromatids attached by the centromere).
Stage 3: G2 Phase (Growth Stage/Preparation for Mitosis)
Meiosis I: Prophase 1
Chromosomes will condense, Centrioles will separate, Nuclear membrane will dissolve and Spindle fibres form
What are Homologous Chromosomes?
Pairs of chromosomes that are similar in shape and size
Genes that control the same inherited traits
*Humans have 23 pairs of homologous
chromosomes 22 autosomes 01 sex chromosome
Synapsis (Prophase 1)
When homologous chromosomes come together to form a tetrad
Tetrads are two chromosomes/four
chromatids
Crossing Over (Prophase 1)
Segments of non-sister chromatids break and reattach to the other chromatids
Location: Chiasmata
Creates variation
Meiosis 1: Metaphase 1
The tetrads migrate towards
the centre of the cell
The tetrads will align their
centromeres across the
middle of the cell (Metaphase plate)
Independent Assortment (Metaphase 1)
How the orientation of
homologous pair align on the metaphase plate random
Use equation 2n to find the
number of combinations.
*Creates variation!
Meiosis 1: Anaphase 1
Homologous chromosomes
move to opposite poles of the
cell
Sister chromatids remain
attached at their centromeres
Meiosis 1: Telophase 1
Nuclear membrane forms
around the chromosomes
Cytokinesis: the cell will
divide to form two cells
The daughter cells are haploid
Meiosis 2: Prophase 2
Centrioles move to opposite ends of the cell
Spindle fibres extend from centrioles to
centromeres
Nuclear membrane breaks down
Meiosis 2: Metaphase 2
Spindle fibers align the
chromosomes along the middle
of the cell at the metaphase plate
Meiosis 2: Anaphase 2
Centromeres divide
Sister chromatids move to
opposite poles of the cell,
now becoming daughter chromosomes.
Meiosis 2: Telophase 2/ Cytokinesis
Chromatids are now at opposite poles of cell
Nucleus membrane and
nucleolus forms for each
daughter cell
Chromosomes disperse and
spindle fibres disappear
What is Fertilization?
The fusion of a sperm and egg to form a zygote.
A zygote is a fertilized egg
What is a gamete?
It’s a sex cell that are in males and females. In males it is sperm cells but females it is egg cells
OVA?
female sex cells or also known as egg cells
Meiosis
two-stage cell division that results in daughter cells having half the amount of chromosomes as the parent cell
Homologous chromosomes
Matching pairs of chromosomes that are similar in size and carry info for some genes
Tetrad
Pair of homologous chromosomes that each have two sister chromatids
Synapsis
the physical paring of homologous chromosomes during prophase I
number of possible combinations of chromosomes depend on the number of chromosome pairs
Gametogenesis
The production of gametes in animals
