Download Meosis Definitions – Let`s talk about sex

UNIT 2: GENETICS
MEIOSIS WARM-UP
Recall that chromosomes are composed of DNA and contain the genetic blueprint for an organism.
Each species has its own unique set of chromosome, and all individuals in a particular species
typically have the same number of chromosomes. Humans have 46 chromosomes. The domestic dog
has 78 chromosomes, the domestic cat has 38 chromosomes, and the mouse that it chases has 40
chromosomes!
Within each individual in a species, every somatic cell (not a sex cell) contains the same number of
chromosomes as every other. Humans (and most other animals) are diploid organisms meaning that
each cell contains two complete chromosome sets.
1.
Where did the two chromosome sets originate? How do parents' genes get passed to their
offspring?
2. The genetic make up of the sex cells of an individual are based on that person’s DNA. Are all
the sperm cells identical in a male? Are all the egg cells identical in a female? How do you know?
(hint: think about the genetics of your sister/brother)
3.
Normal humans carry 46 chromosomes in each cell (2 copies of 23 chromosomes). Why do
we have two copies of each of the genes in our genome?
4.
Can we pick out which genes we want our children to inherit?
5. Human gametes (sex cells) are haploid cells, meaning that they have only one complete set of
chromosomes. If human somatic cells have 46 chromosomes, how many chromosomes do human
gametes have?
6. When fertilization occurs, the haploid sperm cell and haploid egg cell join, producing a fertilized
zygote. This "restores" the diploid chromosome number. How many chromosomes do fertilized
eggs contain? Are fertilized eggs haploid cells or diploid cells?
UNIT 2: GENETICS
Define the following terms:
germ/sex cells
somatic cells
diploid
haploid
meiosis
gamete
genome
chromosome
homologous
chromosomes
gene
allele
phenotype
genotype
sister chromatids
centromere
interphase
cytokinesis
UNIT 2: GENETICS
germ/sex cells
reproductive cells, contain a haploid number of
chromosomes.
somatic cells
not germ cells. These cells contain a diploid
chromosome number
diploid
twice the number of chromosomes in a gamete.
Every cell in the body, except for sex cells,
contains a diploid chromosome number.
haploid
meiosis
number of chromosomes in a gamete – half of the
number of chromosomes in a somatic cell
two-stage cell division in which the chromosome
number of the parental cell is reduced by half.
Gametes form through meiosis.
gamete
sex cells that have a haploid chromosome number
genome
the complete set of instructions contained within
the DNA of an organism
chromosome
the packaging of DNA and proteins
homologous
chromosomes
gene
paired chromosomes similar in shape, size, gene
arrangement and gene information
part of DNA that codes for a protein
UNIT 2: GENETICS
allele
sister
chromatids
alternate forms of a gene, ex. blue eyes and
brown eyes. Alleles are located in the same
position on homologous chromosomes.
the observable trait of an organism, ex. brown
eyes
the alleles (code) an organism contains, ex. allele
for brown eyes and blue eyes
a chromosome and its copy, attached to one
another at the centromere
centromere
structure that holds chromatids together
interphase
the time between nuclear divisions, when a cell
grows and copies its chromosomes to make sister
chromatids
division of cytoplasm that leads to formation of
two new cells
phenotype
genotype
cytokinesis