TOPIC 2-Chap 2.4 Flashcards
Gametes are Haploid/Diploid. Body cells are haploid/diploid.
Gametes are Haploid. Body cells are diploid.
what is a non disjunction of chromosomes
a whole chromosome mutation where there are too little or too many chromosomes
identify and describe 4 types of non disjunction of chromosomes
Aneuploidy-situation where a cell either lacks a whole chromosome or has more than 2 of a chromosome
Monosomy-only one member of a homologous pair present from a normal gamete
Polysomy-three or more rather than 2 chromosomes of a particular type
Trisomy-one extra chromosome
an example of a monosomy mutation is
Turner syndrome only one X chromosome from Ovum
Sexual reproduction occurs when 2 haploid nuclei fuse to form a new _______ cell called a _________.This process is called ________.
Sexual reproduction occurs when 2 haploid nuclei fuse to form a new diploid cell called a zygote. This process is called fertilisation.
In animal cells sex organs that are permanent are usually called ________
In animal cells sex organs that are permanent are usually called the gonads
The male sex organ OF FLOWERING PLANTS is called ______.The female one is _______.The male gametes are ________ and the female gametes are ________.
The male sex organ OF FLOWERING PLANTS is called anthers. The female one is ovaries. The male gametes are pollen and the female gametes are ovules.
IN ANIMALS the male gonads are the ________, which produce the gametes known as sperm/spermatozoa.
The female gonads are called _________ producing female gametes called _____
IN ANIMALS the male gonads are the testes, which produce the gametes known as sperm/spermatozoa.
The female gonads are called ovaries, producing female gametes called ovas .
Describe the process of meiosis
Prophase 1-
each chromosome appears in condensed form with 2 chromatids.Homologous pairs of chromosomes associate with eachother. Crossing over occurs at the chiasmata
Metaphase 1-
the spindle forms and the pairs of chromosomes line up on the metaphase plate
Anaphase 1-
the centromeres do not divide. One chromosome (a pair of chromatids) from each homologous pair moves to each end of the cell. As a result the chromosome number in each cell is half of the original.
Telophase 1-
the nuclear membrane reforms and the cell begins to divide. In some cells this continues to full cytokinesis and there may be a period of brief or prolonged interphase. During this interphase there is NO FURTHER REPLICATION OF DNA.
Metaphase 2-
new spindles are formed and the chromosomes still made up of pairs of chromatids line up on the metaphase plate.
Anaphase 2-
the centromeres now divide and the chromatids move to the opposite ends of the cell
Telophase 2-
nuclear envelope re forms, the chromosomes return to their interphase state and cytokinesis occurs giving four daughter cells each with half the chromosome number of the original diploid cell.
Variation is introduced in 2 ways during meiosis - identify and describe
Independent assortment (random assortment)
the chromosomes that came from the individual parents are distributed into the gametes
Crossing over (recombination)
process that takes place when large multi-enzyme complexes cut and join bits of the maternal and paternal chromatids together. The points where the chromatids break are called the chiasmata.
define diploid and haploid
diploid- a cell with a nucleus containing 2 full sets of chromosomes
haploid-a cell with a nucleus containing one complete set of chromosomes.
define homologous chromosomes
a set of one maternal chromosome and one paternal chromosome that pair up during meiotic cell division
define translocation in terms of mutations
a mutation where part from one chromosome breaks off and re-joins to another completely different chromosome. It is balanced when part of 2 chromosomes swap
Chemicals that are likely to increase the rate of mutation are called ________
Chemicals that are likely to increase the rate of mutation are called mutagens
define gametogenesis
gametogenesis is the formation of the gametes by meiosis in the organs
what are primordial germ cells
the cells that divide by meiosis to ultimately form the sperm and ova
define spermatogenesis
the formation of the sperm in the testes
purpose of oogenesis
to form the ova in the ovaries.
what is external fertilisation
the process of fertilisation in which the female and male gametes are released outside of the parental bodies to meet and fuse in the environment. Typical in aquatic animals.
what is internal fertilisation
the fertilisation of the female gamete which takes place inside the body of the mother
define mating
the process by which a male animal transfers sperm from his body directly into the body of the female
Outline the process of spermatogenesis
DIPLOID primordial germ cell divides by mitosis to form DIPLOID spermatogonia.
These grow until they are big enough to be called primary spermatocytes
Meiosis- the first miotic division results in 2 HAPLOID cells called secondary spermatocytes
Second Meiotic division results in 4 HAPLOID cells called spermatids
Spermatids then differentiate in the tubules of the testes to form spermatozoa
Outline the process of Oogenesis
diploid primordial germ cell divides by mitosis to form diploid oogonia—->Most of the oogonia do not develop further but instead degenerate.
the one that develops and grows is then called the primary oocyte
Oocyte then undergoes meiosis resulting in 2 cells of unequal size called the secondary oocyte (larger one) and the first polar body.
after ovulation meiosis 2 takes place resulting in one HAPLOID ovum and 3 polar bodies
Adaptations of spermatoza
ACROSOME- contains digestive enzyme which can digest the layers of the ovum allowing the sperm head to penetrate.
MIDDLE PIECE- mitochondria tightly packed to provide sperm with ATP for the lashing of the tail
TAIL- allow for sperm to swim towards the egg
ALKALINE Semen- vagina is acidic, protects sperm when entering.
NUCLEUS- contains highly condensed haploid chromosomes, this condensed state of the genetic material reduces the amount of energy needed to transport it
the layer of protective jelly around the unfertilized ovum is known as . . .
Zona Pellucida
__________ is the term used for fertilisation of the ovum in humans.
Conception is the term used for fertilisation of the ovum in humans.
when an egg is fertilised by more than one sperm it is known as ___________
when an egg is fertilised by more than one sperm it is know as POLYSPERMY
The ___________ ___________ is the tough layer that forms around the fertilised ______ to prevent the entry of other sperm.
The FERTILISATION MEMBRANE is the tough layer that forms around the fertilised OVUM to prevent the entry of other sperm.
Outline the process of fertilisation in terms of sperm
sperm approaches oocyte in the oviduct. The acrosome has matured since the sperm left the male reproductive tract
front of sperm touched the zona pellucida of the oocyte and an acrosome reaction is triggered. Enzymes begin to digest layer.
fertilisation happens when the sperm touches the surface of the oocyte and the membranes fuse
sperm’s nucleus quickly decondenses and releases its chromosomes into the oocyte. Meiosis 2 completed forming an ovum.
The male and female chromosomes group together
Cortical granules are released from the oocyte that combines with the zona pellucida to form a tough fertilisation membrane.
state and describe the 2 phases of a plant life cycle
sporophyte generation- diploid and produces spores by meiosis
gametophyte generation-haploid, gives rise to the gametes by mitosis
Describe gametogenesis of the male gamete (pollen) in flowering plants
Pollen grains carry the male gametes.
Each anther consists of 4 pollen sacs where the pollen grain develops.
Each pollen sac contains a large number of microspore mother cells= diploid —-> they divide by meiosis to form
haploid microspores (the gametophyte generation)
Microgametes are formed from microspores by mitosis- one cell envelops the other to form a pollen grain containing 2 haploid nuclei (generative nucleus and pollen tube)
The tube nucleus produces the pollen tube which penetrates through the stigma, style and ovary and into the ovule.
The generative nucleus then fuses with the nucleus of the ovule to form a new individual.
the pollen grain is made up of 2 types of nuclei- state and describe their purpose
generative nucleus- male gamete
tube nucleus- controls growth of pollen tune
Name the female parts of a flowering plant
carpel= stigma, style and ovary
name the male parts of a flowering plant
Stamen=anther and fillament
What is the purpose of the endosperm
energy store for the seed to be used for germination as no photosynthesis can be carried out as the seed is growing under the soil getting no sunlight
Describe the process of double fertilisation
Pollen grain on stigma containing both a generative and a tube nucleus.
Pollen tube forms and the nuclei travel down. The generative nucleus divides by mitosis to form 2 male gametes. Travelling down the tube it penetrates the ovary through the micropyle. One male gamete fuses with the egg to form a zygote while the other fuses with the 2 polar bodies to produce a triploid endosperm.
This is double fertilisation
Describe the process causing the formation of egg cells, the mega gametes in plants
2n megaspore mother cell formed by mitosis
Meiosis 1
meiosis 2- 4 haploid cells (3 degenerate and 1 grows)
megaspore (//young embryo sac)
mitosis 3 (n and n)
mitosis 4 (n* 4)
mitosis 5= mature embryo sac. Contains 2 polar nuclei, 3 antipodal cells, 2 synergids and the female gamete
Describe the process causing the formation of pollen, the microgametes
Pollen mother cell (microspore mother cell)
Meiosis 1
meiosis 2- 4 haploid cells
each nucleus divides by mitosis
pollen grain (microspore)- pollen tube nucleus and generative nucleus
POLLINATION- 2 male gametes produced by the mitosis of the generative nucleus. Each gamete is just a haploid nucleus.
state and describe the 2 phases in the life cycles of plants
sporophyte generation- diploid and produces spores by meiosis
gametophyte generation- results in haploid and gives rise to gametes by mitosis
what do you call a cells ability to develop into all different cell types
TOTIPOTENT
embryonic stem cells that can form most but not all adult cell types are known as
pluripotent embryonic stem cells
the process involving a special type of mitosis with no interphase that results in a mass of small undifferentiated cells is known as
CLEAVAGE
the result of the cleavage stage is a mass of small, identical and undifferentiated cells forming a hollow sphere known as _______________
the result of the cleavage stage is a mass of small, identical and undifferentiated cells forming a hollow sphere known as BLASTOCYST
