MEIOSIS & MUTATIONS
CHROMOSOMES IN HUMAN CELLS
- A human somatic cells have 23 pairs of
chromosomes
-KARYOTYPE is an ordered display of the
pairs of chromosomes from a cell,
- 2 chromosomes in each pair are called:
HOMOLOGOUS chromosomes or
HOMOLOGS
- CHROMOSOMES in a homologous air
are the same length and shape and carry
genes controlling the same inherited
characters.
- GAMETE (sperm or egg) contains a
single set of chromosomes and is thus a
HAPLOID CELL (n).
-SEX CHROMOSOMES determine the sex - Humans have haploid number of 23
of the individual, called X & Y (n=23)
-FEMALES have a homologous pair of X - Each set of 23 consists of 22 autosomes
CHROMOSOMES (XX) and a single sex chromosome.
-MALES have one X and one Y -OVUM (unfertilized egg), the sex
chromosome. chromosome is X.
- remaining 22 pairs of chromosomes are - SPERM CELL, the sex chromosome may
called AUTOSOMES. be either X or Y.
- each pair of homologous chromosomes - Sexual maturity, ovaries and testes
includes one chromosome from each produced HAPLOID GAMETES.
parent. -GAMETES are the only type of human
-46 CHROMOSOMES in human SOMATIC cells produced by MEIOSIS. MEIOSIS
CELL are 2 sets of 23; 1 set from the results in one set of chromosomes in
mother and 1 set from the father. each gamete.
- DIPLOID CELL (2n) has 2 sets of -FERTILIZATION AND MEIOSIS alternate
chromosomes. in sexual life cycles to maintain
- Humans have diploid number is 46 chromosome number.
(2n=46).
, - Division in MEIOSIS I occurs in 4 phases:
Prophase I -> Metaphase I -> Anaphase I
-> Telophase I and Cytokinesis
MEIOSIS reduces the number of
chromosome sets from diploid to haploid.
-Meiosis is precede by the replication of
chromosome.
-Meiosis takes place in two consecutive
cell divisions, called MEIOSIS 1 and
MEIOSIS II.
- 2 cell divisions in MEIOSIS result in 4
daughter cells.
- Each daughter cell has only half as many
chromosomes as the parent cell.
CROSSING OVER and SNAPSIS DURING
PROPHASE I
- After interphase, the sister chromatids
are held together by proteins
called cohesins
- The nonsister chromatids are broken at
precisely corresponding
positions
- A zipper-like structure called the
synaptonemal complex holds the
homologs together tightly
- During synapsis, DNA breaks are
repaired, joining DNA from one
nonsister chromatid to the corresponding
segment of another.
CHROMOSOMES IN HUMAN CELLS
- A human somatic cells have 23 pairs of
chromosomes
-KARYOTYPE is an ordered display of the
pairs of chromosomes from a cell,
- 2 chromosomes in each pair are called:
HOMOLOGOUS chromosomes or
HOMOLOGS
- CHROMOSOMES in a homologous air
are the same length and shape and carry
genes controlling the same inherited
characters.
- GAMETE (sperm or egg) contains a
single set of chromosomes and is thus a
HAPLOID CELL (n).
-SEX CHROMOSOMES determine the sex - Humans have haploid number of 23
of the individual, called X & Y (n=23)
-FEMALES have a homologous pair of X - Each set of 23 consists of 22 autosomes
CHROMOSOMES (XX) and a single sex chromosome.
-MALES have one X and one Y -OVUM (unfertilized egg), the sex
chromosome. chromosome is X.
- remaining 22 pairs of chromosomes are - SPERM CELL, the sex chromosome may
called AUTOSOMES. be either X or Y.
- each pair of homologous chromosomes - Sexual maturity, ovaries and testes
includes one chromosome from each produced HAPLOID GAMETES.
parent. -GAMETES are the only type of human
-46 CHROMOSOMES in human SOMATIC cells produced by MEIOSIS. MEIOSIS
CELL are 2 sets of 23; 1 set from the results in one set of chromosomes in
mother and 1 set from the father. each gamete.
- DIPLOID CELL (2n) has 2 sets of -FERTILIZATION AND MEIOSIS alternate
chromosomes. in sexual life cycles to maintain
- Humans have diploid number is 46 chromosome number.
(2n=46).
, - Division in MEIOSIS I occurs in 4 phases:
Prophase I -> Metaphase I -> Anaphase I
-> Telophase I and Cytokinesis
MEIOSIS reduces the number of
chromosome sets from diploid to haploid.
-Meiosis is precede by the replication of
chromosome.
-Meiosis takes place in two consecutive
cell divisions, called MEIOSIS 1 and
MEIOSIS II.
- 2 cell divisions in MEIOSIS result in 4
daughter cells.
- Each daughter cell has only half as many
chromosomes as the parent cell.
CROSSING OVER and SNAPSIS DURING
PROPHASE I
- After interphase, the sister chromatids
are held together by proteins
called cohesins
- The nonsister chromatids are broken at
precisely corresponding
positions
- A zipper-like structure called the
synaptonemal complex holds the
homologs together tightly
- During synapsis, DNA breaks are
repaired, joining DNA from one
nonsister chromatid to the corresponding
segment of another.
