The Chromosomal Basis of Heredity (A)-ppt Flashcards
- it is the series of events that take place in a cell leading to its replication
the cell cycle
types of cells:
a. prokaryotic
b. eukaryotic
- unicellular
- lack a defined nucleus
- e.g. monerans, bacteria, cyanobacteria
prokaryotic
- multicellular
- have a defined nucleus
- e.g. plant, animal, protist, fungi
eukaryotic
________ is the method by which prokaryotes produce new individuals that are genetically identical to the parent organism.
Binary fission
Eukaryotes have two major
types of cell division:
a. mitosis
b. meiosis
- is used to produce new body cells for growth and healing
Mitosis
- is used to produce sex cells (eggs and sperm)
meiosis
Depending on cell type, typical eukaryotic cells have a cell
cycle of ______ hours, which is divided into phases.
16 to 24
DNA means
Deoxyribonucleic acid
- is a molecule that carries genetic information in living organisms. It looks like a twisted ladder (double helix) and is found
inside the nucleus of our cells.
DNA
- the basic physical unit of heredity and it is passed on from generation to generation in cells
gene
- determines the characteristics of the individuals
produced.
gene
the entirety of genes or genetic material that is present in a cell or organism
genome
A ________ contains all of the information needed to build and make an organism function.
genome
are thread-like structures present in the nucleus, which carries genetic information from one generation
to another.
chromosome
Chromosome means: chroma – ______; some - ____, that refers to its staining ability by certain dyes
colour; body
_______ in 1842, first observed the rod-like structure present in the nucleus of the plant cell.
Karl Nägeli
It is clearly visible only when the cell is undergoing division.
chromosome
At ______, chromosomes are visible as thin chromatin fibres present in the nucleoplasm.
interphase
During cell division, the chromatin fibres condense and _________ are visible with distinct features.
chromosome
Chromosome Structure:
a. chromatids
b. telomere
c. centromere
- one of the longitudinal subunits of a replicated chromosome joined to its sister chromatid at the centromere
chromatids
- a region of repetitive DNA at the end of chromosomes, which protects the end of the chromosome from destruction
telomere
- the point at which two parts chromatids of a chromosome join and at which the spindle fibers are attached during cell division
centromere
Types of Chromosomes based on the position of the centromere:
a. metacentric
b. sub-metacentric
c. acrocentric
d. telocentric
- centromere in middle forming two equal arms
metacentric
- centromere placed near to one end resulting in one shorter and one long arm
sub-metacentric
- centromere placed close to one end forming one extreme short and one extreme long arm
acrocentric
- terminally placed centromere
telocentric
It is the growth cycle of an individual cell consisting of the following phases:
Interphase & Mitotic Phase.
- produce identical cell
cell division
phases of cell cycle:
a. interphase
b. mitotic phase
- The period between mitotic
divisions - that is, G1, S and G2 - non-dividing phase
interphase
Metabolic changes prepare the cell
for division.
G1 Phase
The cell increases in volume
(nucleus & cytoplasm are enlarging
toward mature size) by imbibing
water & nutrients & building new
protoplasm
G1 Phase
Cytoplasmic organelles are formed,
e.g., endoplasmic reticulum, golgi
apparatus, ribosomes,
mitochondria, & chloroplast
G1 Phase
DNA synthesis replicates the
genetic material.
S Phase
Each chromosome now consists of
two sister chromatids.
S Phase
There is active synthesis of RNA &
proteins necessary for
chromosome synthesis.
G2 Phase
Mitotic spindles are also starting to
be formed.
G2 Phase
Cell prepares itself for mitosis by
synthesizing needed components.
G2 Phase
The process by which a cell
divides to form two new cells,
either to produce identical cells
(mitosis) or to produce cells with
half the number of chromosomes
(meiosis)
cell division
Two types of cell division:
- Mitosis
2.Meiosis
- process of cell division by which one cell results in two daughter cells, each with a set of chromosomes identical to that of the parental cell.
mitosis
mitosis is important for:
- replacement of worn out or damaged tissues
- repair of injuries,
- multicellular growth and development by
increasing the number of cells
Mitotic division occurs in two parts:
a. karyokinesis
b. cytokinesis
- (nuclear division) (having the
prophase, metaphase, anaphase, and telophase)
karyokinesis
- (cytoplasmic division)
cytokinesis
prophase:
a. early prophase
b. late prophase
- Chromosomes are condensed and
consist of 2 sister chromatids - The nuclear membrane begins to break down and nucleoli start to disappear
- Spindle fibers appear
early prophase
- The centromere joins each pair of sister
chromatids to the spindle fiber - Nucleoli & nuclear membrane
completely disappears by late prophase
late prophase
The spindle fibers grow and forms
attachments to the chromosomes on the opposite sides of the centromere
metaphase
- The chromosomes line up along the middle of the cell (_____/equatorial plate)
metaphase
The chromatids in each chromosome separate from each other except at the centromere
metaphase
In plants, the centromeres and their accompanying centrioles are generally missing although spindles are nevertheless present
metaphase
The centromeres become functionally double
anaphase
Centromeres divide to create two chromosomes instead of a pair of attached chromatids
anaphase
Spindle fibers shorten due to depolymerization, pulling the sister chromatids apart and
drawing them to the opposite poles of the cell. Once they have separated, they are
individual chromosomes.
anaphase
Upon reaching the opposite poles, the chromosomes regroup into two nuclear structures
telophase
nuclear envelopes reassemble and surround each set of daughter chromosomes while spindle fibers disassemble
telophase
nucleoli reappear inside the newly formed nuclei
telophase
chromosomes decondense in the daughter cells to become chromatin and the cells are once again in Interphase
telophase
The chromosomes begin to uncoil & lengthen & finally lose their visible identity
telophase
Usually follows mitosis or
begins during telophase.
cytokinesis
In plant tissues, the cytoplasm
is divided via cell plate
formation where separation
starts from the inside of the
cell towards the periphery
cytokinesis
The cytoplasm is divided
between the two cells forming
two daughter cells.
cytokinesis
sequence of two cell division, each cell divides twice while the
chromosomes are duplicated only once, resulting gametes have
only half the chromosome number of the original cell
meiosis
meiosis stages:
a. Meiosis I (reduction division); (PMAT)
b. Meiosis II (equational division);
(PMAT)
one of a pair of chromosomes
with the same gene sequence,
loci, chromosomal length, and
centromere location
Homologous chromosome
– pair of two homologous
chromosomes formed by synapsis
during the early stages of meiosis.
Bivalent
– is the group of four sister
chromatids inside the homologous
chromosome pair
Tetrad
A bivalent consists of ______ pair/pairs sister
chromatid/chromatids and ______ pair/pairs of
homologous chromosomes.
two; one
the pairing of two chromosomes that occurs during meiosis
synapsis/ syzygy
The exchange of corresponding parts between non-sister chromatids of homologous chromosomes producing a
new combinations is called
_______________
crossing over
point of contact between two non-sister chromosomes belonging to the homologous chromosomes
chiasma
are chromosomes other than the sex chromosomes. In humans, there are 22 pairs of _________.
autosomes
– A specific variation of a gene. Example: Blue eyes, green eyes, type A blood, black skin,
white skin
allele
refers to the period of rest between meiotic divisions, similar to the interphase stage
in mitosis
interkinesis
