GENETICS(cell part 2) Flashcards
Chromosome means:
chroma - color; some - body
seen during metaphase stage of mitosis
Chromosome
in 1875 discovered thread-like structures which appeared during cell division.
E. Strasburger
coined the term chromosome first time in 1888.
Waldeyer
is the number of chromosomes
found in somatic cell and is represented by 2n (Diploid).
somatic chromosome number
half of the somatic chromosome
numbers and represented by n (Haploid).
gametic chromosome number
The two copies of chromosome are ordinarily identical in morphology,
gene content and gene order, they are known as
homologues chromosomes.
that control characters other than sex characters or carry genes for somatic characters.
Autosomes
Chromosomes involved in sex
determination.
Sex chromosomes (Gonosomes)
Humans and most other mammals have two sex chromosomes X &
Y, also
heterosome
body cells of animals are
diploid.
have only one copy of each chromosome.
haploid cell
have two homologous copies of each chromosome.
diploid cell
normally measured at mitotic
metaphase
size of chromosome
Each chromosome has two arms
p (the shorter of the two) and q (the longer).
usually observed at anaphase, when the position of primary constriction (centromere) determines chromosome
shape.
Chromosome shape
can be terminal, sub-terminal or
median in position.
constriction or centromere
Diploid organisms have two copies of each chromosome (except
sex chromosomes
is the most suitable stage for studies on chromosome morphology.
Mitotic metaphase
Chromosomes are thin, coiled, elastic, thread-like structures during the
interphase
longitudinally divided
into two identical parts each of which
chromatid
Both the chromatids of a chromosome appear to be joined together at a
point known
centromere.
separate from each other
during mitotic anaphase
two chromatids of chromosome
the chromatids of homologous chromosomes are known as
non-sister chromatids
Each chromosome has a constriction
point called the
centromere
, which divides the
chromosome into two sections or arms.
Kinetochore
The p arm is named for ___ meaning”small”;
“petite”
The two ends of a chromosome
are known
telomeres
they play critical roles in chromosome
replication and maintenance of
chromosomal length.
telomeres
The telomeric region of
chromosome is made up of
repetitive sequence of
t and g bases
Useful in identifying a
chromosome from a set.
SECONDARY CONSTRICTION
The chromosomal region between
the secondary constriction and
nearest telomere and chromosomes
that possess this region called
satellite chromosome or sat
chromosome.
A small chromosomal segment
separated from the main body of the
chromosome by a secondary
constriction is called
Satellite
The chromosomes are the longest and thinnest during interphase
Size of the chromosome
smallest and thickest during mitotic
metaphase.
Chromosomes
NOT proportional to the number
Chromosome size
Chromosomes are classified according
to the centromere position:
- At one end: Acrocentric
- Closer to one end: Submetacentric
- Middle: Metacentric
- Terminal: Telocentric
midway between each end and thereby two arms are roughly equal in length.
Metacentric Chromosome
Metacentric chromosome take _during anaphase.
V shape
is located on one side
of the central point of a
chromosome.
Submetacentric Chromosome
Submetacentric chromosome may
be__shaped during anaphase.
J or L shape
located close to one end of chromosomes.
Acrocentric Chromosome
(The “acro-“ in acrocentric
refers to the Greek word for
“peak”
arm is so short that is
hard to observe, but still present.
p (short)
Acrocentric chromosome may be
__ during anaphase.
rod shape
located at one end of chromosome (at
terminal part of chromosome)
Telocentric Chromosome
Telocentic chromosome may
be ____ during
anaphase.
rod shape
- Acentric: without any centromere
- Mono centric: with one
centromere - Dicentric : with two centromeres
- Polycentric: with more than two
centromeres
- Acentric: without any centromere
- Mono centric: with one
centromere - Dicentric : with two centromeres
- Polycentric: with more than two
centromeres
The DNA double helix in the cell
nucleus is packaged by special
proteins termed
histones.
The formed protein/DNA complex is
called
chromatin.
The structural entity of chromatin is
the
nucleosome
The DNA + Histone =
Chromatin
Histone can be grouped into
five major classes:
H1/H5,H2A, H2B, H3, and H4
These are organized into two
super-classes as follows:
- Core histones – H2A,
H2B, H3 and H4 - Linker histones – H1 and
H5
Basic unit of DNA packaging in eukaryotes
nucleosome
Transcriptionally inactive
heterochromatin
Often (but not always) under active transcription
euchromatin
Regular sequence of events
that produce new cells.
cell cyle
4 distinct phases:
- G1
- S
- G2
Pre-requisite stage before a cell
undergoes mitosis
INTERPHASE
This phase is where the cell spends
most of its time, specifically 20 hours
a day.
interphase
Where the cell grows and functions normally
gap 1phase (g1)
Where the cell grows and functions normally
gap 0 phase (g0)
Cell cycle activities may be temporarily or permanently suspended
gap 0 phase (g0)
can occur in S phase.
Genetic Mutation
makes DNA strands linear, straight, long, uncoiled, thin, and not condensed.
HISTONE:
makes DNA strands coiled, crumpled, and condensed to avoid unnecessary replication/duplication
PROTAMINE:
Period of preparation for mitosis
gap 2 phase (g2)
cyclin derived kinase-1
CDK-1
cell division cycle expressed gene;
CDC-2
pre-maturation promoting factors
pre-MPF
After interphase, the cell would proceed to ___
(direct process) which is divided into four stages: PMAT
KARYOKINESIS – MITOSIS
Karyokinesis came from two Greek words:
Karyon (nucleus) and
Kinesis (movement);
Mitosis came from greek word
Mitos (thread: pertaining to
chromatin) and Osis (process/condition/status).
Period of cell division
mitosis
The first phase of mitosis,
prophase
increases making the DNA strands of the cell start to condense, to contract,
Protamine concentration
stage which occurs before metaphase.
prometaphase
chromosomes
condense and move
together, aligning in the
center of the dividing cell.
metaphase
Each is attached by
____ extending from the centromere to the centriole,
forming the ____
microtubules, mitotic spindle.
separates
the duplicated genetic
material carried in the
nucleus of a parent cell into
two identical daughter
anaphase
Each daughter cell
receives half of all doubled
chromosome material and thus
maintains the same number of
chromosomes as the mother
cell.
telophase
Indirect process required by Mitosis; Condition of cytoplasm division.
cytokinesis
is identical and
equal of the parent cell.
chromosomal configuration of the daughter cells
+ 2 X allosomes.
female
+ 1 X and 1 Y allosomes
male
The cell division that takes place in the germ cells to generate
male and female gametes, sperm and egg cells, respectively.
meiosis
The cells produced are HAPLOID,
meiosis
to
reduce the number of chromosomes to the haploid number of
23.
meiosis I and meiosis II,
meiosis Came from two Greek words:
Meion (to reduce, to diminish,
a lessening) and Osis (process/condition/status);
two sets of PMAT are required in
this process:
Meiosis I (M1) and Meiosis II (M2)
Each of the PMAT of meiosis is intervened by a real
resting stage called
interkinesis
which lasts for 2 to
3 hours.
interkinesis
chromosomes are
long, thin, uncoiled, and
non- contracted due to
an increase in histone
concentration.
Leptotene/Leptonema
synapsis of
homologous chromosomes
Zygotene/Zygonema-
which would result to a crossing over or an exchange of genetic material
between the maternal and paternal
homologous chromosomes
Pachytene/Pachynema-
where the egg cell
will stop dividing for the first
time.
Diplotene/Dictyate-
This is
the movement or
parting of two
strands.
Diakinesis-
The daughter cell that
receives little amount of
cytoplasm is called a
polar body
Has a similar process as mitosis.
meoisis ii
parent cell is diploid (44
chromosomes + 2 allosomes)
before m1
daughter cells are haploid (22
chromosomes + 1 allosome)
after m1
is a cell division that produces two diploid cells
mitosis
produce 4 haploid cells
meiosis
Process of generating female
seed
oogenesis
Process starts from the 5
the month of gestation to up to 44
years of age
oogenesis
3 different germ layers
ectoderm
, endoderm
mesoderm)
do not undergo lyonization, retain active X
Primordial Germ Cell (PGC)
start to multiply via mitosis from the 7
th week of gestation to the 5th month
Oogonium
The last set of oogania during the 5
th month will give rise to
primary oocyte
is required to overcome the first arrest state and to
resume meiosis I
Puberty
regularly monthly for regularly menstruating
females
OVULATION
Starts at age 9 and ends at 44
ovulation
3 region of the fallopian tube
Isthmus (constricted)
Ampulla (dilated)
Infundibulum with fimbrae (terminal)-
- most common site of fertilization and most common site of
ectopic pregnancy
Ampulla (dilated)
the most common site of ectopic
pregnancy)
Infundibulum with fimbrae (terminal)-
Requires only 74 days for each cycle
spermatogenesis
Conversion commences at age 10 (onset of puberty)
spermatogenesis
13 days to 22 days because of arrest state
spermatidogenesis
primary spermatocyte enter first and last arrest during prolonged prophase I, dictyate stage (stays in arrest
for 22 days)
meiosis 1
13.5 days and Spermatid to sperm like
spermiogenesis
Immature, immotile,incapableof fertilization
spermiation
Act of releasing mature, motile, but incapable of fertilization sperm cells
ejaculation
Period of conditioning
capacitation
Nourish the PGC from 3rd week to year 10
sertoli ceels
Participate in the blood-testis barrier
sertoli cells
Synthesis of androgen-binding protein
sertoli cells
Synthesis of anti-Mullerian Hormone or Mullerian inhibitin substance
sertoli cells
Synthesize and secrete
testosterone/androge n as early as 8th week of gestation;
leydig cell
