Chromosome and Karyotype Flashcards
Each chromosome is a part of a pair –>
one from mom & one from dad
Homologous chromosomes are:
- same size
- same centriomes positions
- same genes
Versions of the genes (alleles); don’t…
have to be the same (hair colour, eye colour, etc)
Humans have how many pairs of homologous chromosomes?
23 pairs
22 pairs of homologous chromosomes are
autosomes
1 pair of homologous chromosomes are
sex chromosomes
Girl Xx
Boy XY
what is a karyotype?
picture of all 23 pairs of homologous chromosomes
in a karyotype how are the chromosomes lined up?
big to small 1-22 then 23rd pair
Diploid
- contains 2 sets of chromosomes
- 1 from mom and 1 from dad
- 2n= 46
haploid
- contains 1 set of chromosomes
- humans= 23 chromosomes= N
- sperm & egg
reduction division
makes gametes (sex cells), each have 23 chromosomes
meiosis is necessary for…
sexual reproduction
two divisions:
meiosis I then meiosis II
all cells in your body are
diploid
sex cells are
haploid
begin cell division with
interphase (G1, S, G2)
- replicate and copy DNA and chromosomes
meiosis–>
making gametes–>sperm & egg
spertmatogenesis
making sperm
In testes –>
cells will go through meiosis –> sperm
sperm matures in the
epididymus
sperm development begins at birth and ends at
death
potential of millions of sperm made when?
everyday
Oogenesis-
making eggs
in ovaries –>
cells will go through meiosis –> eggs
make 1 big egg cell =
haploid = 23 chromosomes
3 polar bodies
very little cytoplasm –> dry up –> 1
Follicles
craters withing the ovary where the eggs develop
–> 400,000
women release about how many eggs in a lifetime?
400 eggs
chromosomal mutations involve changes in the whole
chromosome
chromosomal mutations may change the number of
chromosomes or even number of genes on the chromosome
Chromosomal mutations are caused by
mutagens, heredity, errors in meiosis, etc.
nondisjunction
failure of chromosomes to seperate properly
what does nondisjunction cause?
aneuploidy-abnormal chromosome #
trisomy
extra chromosome
monosomy
missing chromosome
down syndrome
extra #21
turner’s syndrome
missing sex chromosome
XO= female
Klinefelter’s syndrome
extra sex chromosome
XXY = male
how many chromosomes are present (replicated)?
[interphase]
10
how many chromatids are present after DNA replication? [interphase]
20
what is a gene?
a segment of DNA info that codes for a trait
where is a gene located?
DNA (chromosome)
Every gamete has 2 sets of genes. Where do these genes come from?
mom & dad
what is a gamete?
sex cell
the goal of meiosis is to ______ the 2 sets of genes so that each gamete (sex cell) contains just one set of ______
separate
chromosomes
This way, in fertilization, when the sperm meets the egg, we end up with
2 complete sets of genes
Chromosomes from the father that correspond and match chromosomes from the mother are called ______
homologous chromosomes
Chromosomes carry
many different genes
Homologous chromosomes carry the same types of _______
genes
but the trait on the father’s chromosomes may be different than the trait on the chromosome
from the mother’s
a cell that contains both sets homologous chromosomes is said to be ______, meaning ______ sets
- diploid
- 2
a gamete that contains a single set of genes is said to be _____ meaning ______ set
- haploid
- 1
what is the diploid number?
46= 2n
what is the haploid number?
23 = n
after meiosis I there are ______ new cells w/ ______ chromosomes of the original cell
-2
-5
two ______ cells results with sets of chromosomes and alleles that are ______ from each other and different from the OG diploid cell
- haploid
- different
how does crossing over result in new combinations of alleles?
more variety of genes
at the end of meisosis II there are ______ new cells each with ______ the chromosome of the original cell
-4
-1/2
what are 2 events in meiosis that are the most responsible for the genetic variety found in gametes?
crossing over
independent assortment
