Unit c1: Cell division, genetics, and molecular biology Flashcards
apoptosis
programmed cell death. removes unwanted tissue and prevents cancer
cell cycle
Interphase:
- G1 stage: growth
- S stage : synthesis of DNA
- G2 stage: growth
mitotic stage:
- Mitosis: division of nucleus
- Cytokinesis : division of the cytoplasm
chromatid
One DNA molecule
chromosome
Chromosomes are composed of chromatin.
* Chromatin is a combination of DNA and protein,
mostly histones.
Chromosomes are either:
Dispersed and extended in a non-dividing cell, so that
the DNA is available for gene expression
a) or
b) Condensed into compact, coiled form for cell division
* Histones play a role in tightly coiling the DNA
cytokinesis
the division of the cytoplasm, follows mitosis. results in two daughter cells identical to the mother cell
G1 stage
cell doubles its organelles and accumulates material for DNA synthesis
G2 stage
cell synthesizes proteins for cell division
interphase
is the stage of the cell cycle where the cell grows, carries out normal functions, and prepares for division by replicating its DNA. It consists of three phases: G₁ (growth), S (DNA synthesis), and G₂ (preparation for mitosis).
mitosis
the division of the nucleus, follows interphase. sister chromatids separate into daughter chromosomes
S stage
DNA synthesis occurs. DNA doubles. each chromosome changes from one DNA molecule to two identical DNA molecules
somatic cell
body cells that continue to undergo cell division throughout life
anaphase
Centromeres divide, and sister chromatids are moved
to opposite poles of the cell by spindle fibers
cell plate
A structure in plant cells that forms during cytokinesis, eventually developing into the new cell wall between daughter cells.
centrioles
A small, tube-like structure in animal cells that helps pull chromosomes apart during cell division.
centromere
The part of a chromosome that holds the two sister chromatids together and helps them attach to spindle fibers during cell division.
chromatin
Loose, thread-like DNA found in the nucleus that condenses into chromosomes during cell division.
cleavage furrow
A groove that forms in animal cells during cell division, pinching the cell in half to create two new cells.
diploid
A cell that has two sets of chromosomes, one from each parent (symbolized as 2n)
DNA
A molecule that carries genetic information, found in the nucleus of cells, and determines an organism’s traits.
haploid
A cell that has only one set of chromosomes, half the number of a diploid cell (symbolized as n).
histones
Proteins around which DNA wraps to help organize and pack it into a compact structure called chromatin.
metaphase
Spindle fibers are fully formed and attached to the
chromatids
* Centromeres of chromosomes are aligned at the
metaphase plate (the equator of the cell)
metaphase plate
The imaginary line where chromosomes align during metaphase of cell division, preparing to be separated into daughter cells.
nuclear envelope
The double membrane that surrounds and protects the nucleus in a cell, controlling what enters and exits.
prophase
Nuclear envelope breaks apart; nucleolus
begins to disappear
* Chromatin condenses so that the chromosomes
become visible
* Each chromosome = two identical sister chromatids
held together at the centromere
* Spindle fibers begins to form between the
centrioles and the centromeres
spindle fibers
Protein structures that form during cell division and help separate chromosomes by attaching to their centromeres and pulling them apart.
telophase
- Spindle fibers disappear
- Daughter cells are forming
- Nuclear envelope reappears
- Nucleolus appears in each daughter cell nucleus
Near the end of telophase: - Chromosomes turn back into chromatin
- Cytokinesis (division of cytoplasm) begins
crossing-over
A process during meiosis where homologous chromosomes exchange sections of their DNA, leading to genetic diversity in offspring.
gametes
Reproductive cells (sperm in males and eggs in females) that have half the number of chromosomes, combining during fertilization to form a new organism.
genetic variation
Differences in DNA among individuals in a population, which contribute to diversity in traits and help with adaptation to changing environments.
homologous pair
A set of two chromosomes, one from each parent, that are similar in shape, size, and genetic content.
independent assortment
The random distribution of different chromosomes into gametes during meiosis, leading to genetic variation.
interkinesis
A short resting phase between meiosis I and meiosis II, where no DNA replication occurs.
meiosis
A type of cell division that reduces the chromosome number by half, producing four genetically diverse gametes (sperm or egg cells).
synapsis
The process during meiosis where homologous chromosomes pair up and align closely with each other.
1 oocyte
An immature egg cell in females that is formed during fetal development and remains dormant until puberty, where it may resume development during ovulation.
1 spermatocyte
An immature sperm cell that undergoes meiosis to eventually form four sperm cells. It is produced during male gamete development.
2 oocyte
The egg cell formed after the primary oocyte undergoes the first division of meiosis. It is released during ovulation and can be fertilized by a sperm cell.
2 spermatocyte
A cell formed after the primary spermatocyte undergoes the first division of meiosis. It will divide further to produce spermatids, which develop into sperm cells.
dizygotic twins
Also known as fraternal twins, they are twins that develop from two separate eggs fertilized by two different sperm cells, resulting in genetically distinct siblings.
monozygotic twins
Also known as identical twins, they are formed when a single fertilized egg splits into two embryos, resulting in genetically identical siblings.
polar body
A small cell produced during the division of an oocyte (egg cell) that typically does not develop into a viable egg, and is reabsorbed by the body.
sperm
The male reproductive cell responsible for fertilizing the female egg cell (ovum) to create a zygote. It carries half of the genetic material needed for reproduction.
spermatid
– An immature male reproductive cell that results from the second division of meiosis. It develops into a mature sperm cell through a process called spermatogenesis.
spermatogenesis
The process by which sperm cells are produced in the testes, involving the division and maturation of germ cells into mature sperm.
zygote
The fertilized egg formed when a sperm cell from the male combines with an egg cell from the female, containing a full set of chromosomes (half from each parent).
allele
Different forms of a gene that determine specific traits, such as eye color or blood type. Each individual has two alleles for each gene, one inherited from each parent.
dihybrid cross
A genetic cross between two organisms that involves two traits, each with two alleles, to study how they are inherited together.
dominant
An allele that expresses its trait even when only one copy is present, overpowering the effect of a recessive allele.
F1 generation
The first generation of offspring produced from a cross between two parent organisms.
F2 generation
The second generation of offspring, produced by breeding two individuals from the F1 generation. This generation shows the results of genetic recombination and segregation.
gene
A segment of DNA that carries instructions for a specific trait or function, and is passed from parent to offspring.
genotype
alleles that are responsible for
an individual’s appearance
heterozygous
If the two alleles are different, the individual is said to be heterozygous.
homozygous
If the two alleles are the same, the individual is said to
be homozygous
law of independent
assortment
A principle stating that genes for different traits are inherited independently of each other, meaning the inheritance of one trait doesn’t affect the inheritance of another.
law of segregation
Even though individuals have two alleles for each trait,
their gametes only have one allele for each trait.
locus
The specific location or position of a gene on a chromosome.
monohybrid cross
A monohybrid cross is a genetic cross between two individuals that examines the inheritance of one specific trait. For example, if you’re studying flower color, a monohybrid cross would focus only on how this single trait (flower color) is passed from parents to offspring. The parents could have different versions (alleles) of the gene for that trait, like purple or white. By tracking the inheritance of these alleles, we can predict the possible outcomes for the offspring’s trait.
phenotype
an individual’s appearance
* may include physical, microscopic, and
metabolic characteristics
Punnett square
A diagram used to predict the genetic outcomes of a cross between two organisms, showing the possible allele combinations for offspring.
recessive
An allele that only expresses its trait when two copies are present (one from each parent). It is masked by a dominant allele if only one is present.
testcross
A genetic cross between an individual with an unknown genotype (but showing a dominant trait) and an individual with a homozygous recessive genotype, used to determine the unknown genotype.
autosomal chromosomes
An autosomal chromosome is any
chromosome other than the sex
chromosomes (which are X or Y in humans).
autosomal dominant disorder
A genetic disorder caused by a mutation in just one copy of a gene on an autosomal chromosome. Only one affected parent is needed to pass the disorder to their offspring. Examples include Huntington’s disease and Marfan syndrome.
autosomal recessive disorder
A genetic disorder that occurs when an individual inherits two copies of a mutated gene, one from each parent, on an autosomal (non-sex) chromosome. Examples include cystic fibrosis, sickle cell anemia, tay Sachs, phenylketonuria
carrier
An individual who has one copy of a recessive allele for a genetic disorder but does not show symptoms of the disorder, as the dominant allele masks the effect. They can pass the allele to their offspring.
pedigree
A pedigree is a chart of a family’s history
with regards to a particular genetic trait
.* Males are shown as squares
* Females are shown as circles
* Affected individuals are shaded ◼⚫
sex chromosomes
The pair of chromosomes that determine an individual’s sex. In humans, females typically have two X chromosomes (XX), and males have one X and one Y chromosome (XY).
codominance
Codominance occurs when alleles are
equally expressed in a heterozygote.
* Example: roan cattle
* Have areas of red fur and areas of white fur
* Example: blood type AB
* Has characteristics of both Type A and Type B blood
(cow baby)
incomplete dominance
Incomplete dominance occurs when the
heterozygote has an intermediate phenotype
between the two homozygotes.
* Example 1: A curly-haired person reproduces with a
straight-haired person.
➢ Their children will have wavy hair.
* Example 2: Two wavy-haired people reproduce and
have an expected offspring phenotypic ratio of 1:2:1.
➢ 1 curly hair: 2 wavy hair: 1 straight hair
multiple allele inheritance
When a trait is controlled by multiple alleles,
the gene exists as more than two alleles.
* Example: There are the three alleles responsible
for blood types in humans.
IA = has A antigens on red blood cells
* IB = has B antigens on red blood cells
* i = has neither A nor B antigens on red blood cells
* IA is dominant over i
* IB is dominant over i
* IA and IB are codominant
polygenic inheritance
Polygenic inheritance occurs when a trait is
governed by multiple genes.
* Dominant alleles have a quantitative effect on
the phenotype, and these effects are additive.
* The result is a continuous variation of
phenotypes.
* An example of this is skin colour.
* More than 100 different genes influence skin colour.
* Other examples include height and weight.
