M5 - Heredity Flashcards
explain the mechanisms of reproduction that ensure the continuity of a species, by analysing sexual and asexual methods of reproduction in a variety of organisms, including but not limited to:
animals
Animals:
Advantages of external and internal fertilisation
Internal: takes place inside the body of the female and involves mate attraction and copulation. As a result, fewer offspring are produced.
- More protection against outside environments and predators.
- Greater chance of successful fertilisation
External: where a male organism’s sperm fertilises a female organism’s egg outside of the female’s body.
- Results in the production of a large number of offspring.
- Easier to find mates as the gametes released can drift.
explain the mechanisms of reproduction that ensure the continuity of a species, by analysing sexual and asexual methods of reproduction in a variety of organisms, including but not limited to:
Plants
Plants: asexual and sexual reproduction
Sexual
Flowering plants (angiosperms) reproduce sexually
Stamens are the male reproductive parts and on the filament, there’s an anther, which contains sperm cells of a plant (pollen)
The carpel is the female reproductive part of a plant, it has an ovary on the bottom, a style (stalk) and stigma at the top which is sticky so pollen can stick to it. When the eggs are fertilised by pollen by the pollinators (bees), it will develop into the fruit of the plant
Asexual
Non flowering plants (gymnosperms) reproduce asexually using cones
Female cones grow in the upper branches, the ovule in each scale can be fertilised by wind- blown pollen
Male cones grow in the lower branches, they can release pollen
After fertilisation, a diploid zygote forms which forms a seed which grows into a mature tree
explain the mechanisms of reproduction that ensure the continuity of a species, by analysing sexual and asexual methods of reproduction in a variety of organisms, including but not limited to:
Fungi
Fungi: budding, spores
Spores (multicellular fungi)
Fungi reproduce by releasing spores into the environment, which germinate in a new location and form a new fungus
Asexual reproduction involves spores produced by mitosis
Sexual reproduction involes spores producd by meiosis
Budding (unicellular fungi)
Yeasts reproduce asexually using budding.
A bud will form on the side of the cell, then nuclear division provides each cell with genetically identical nucleus
After the bud is nearly as large as the parent, cytokinesis occurs (separation of the cytoplasm to form 2 cells)
explain the mechanisms of reproduction that ensure the continuity of a species, by analysing sexual and asexual methods of reproduction in a variety of organisms, including but not limited to:
bacteria and protists
Bacteria: binary fission
Bacteria have one chromosome which contains a region called the origin of replication, where the chromosome replicates
After the origin is duplicated, one copy of the origin moves to the opposite end of the cell
Once the entire chromosome has been duplicated, the cells begins to elongate to get ready to divide into two
It then undergoes cytokinesis which results in the formation of two daughters cells that are genetically identical
Protists: binary fission, budding
analyse the features of fertilisation, implantation of pregnancy and birth in mammals
Fertilisation and implantation
- The male and female copulate
- Ejaculation causes semen from the male to move into the female vagina
- The sperm travels through the female reproductive tract - passing through the cervix, into the uterus, then into the fallopian tubes
- A single sperm fertilises each available egg, resulting in one or more zygotes
- The zygote grows through mitosis as it travels down the fallopian tubes to the uterus. It begins to develop into an embryo
- The embryo implants into the endometrial wall of the uterus to continue developing. It is nourished by the placenta
- It grows into a foetus then a baby
analyse the features hormonal control of pregnancy and birth in mammals
Hormonal control
FSH - made by the pituitary gland, located in the ovaries, promotes development of follicle and secretion of oestrogen
LH - made by the pituitary gland, located in the ovaries, promotes ovulation, development of corpus luteum, and secretion of progesterone
Oestrogen - made by the ovaries, located in the body, promotes the development of the endometrium, and the menstrual cycle. Development of female
features and behaviour.
Progesterone - made by the ovaries, located in the uterus, prepares uterus and maintains pregnancy by maintaining the endometrium
GnHR - made by the hypothalamus, located in the pituitary glands, causes pituitary glands to release FSH and LH.
HCG - made by embryo, located in the ovaries, maintains corpus luteum for production of
progesterone and oestrogen, stopping ovulation and maintains uterus lining.
model the processes involved in cell replication, including but not limited to: mitosis and meiosis
Mitosis
- Interphase - growth stage, synthesis DNA and results in cells have x shaped chromosomes (chromatids)
- Prophase - chromosomes becomes visible, nuclear envelope begins to break down, mitotic spindle begins to form
- Metaphase - chromosome align in the middle of the cell and the centromeres become attached to a spindle fibre
- Anaphase - two sister chromatids of each chromosomes move away from each other towards opposite sides of the cell (daughter chromosomes)
- Telophase - the cell prepares to split into two by forming a nuclear envelope around each set of chromosomes and the spindle disappears
- Cytokinesis - divides cytoplasm into two forms two daughter cells
Meiosis
- Creates haploid gametes
- Have two rounds of cell division: meiosis i and meiosis ii
- DNA replication first occurs
- Then during meiosis i, homologous parts of chromosomes loosely pair up and line up in the centre of the cell. Then it gets separated into two cells
- During meiosis ii, chromosomes line up again in the centre. Microtubules then separate the sister chromatids of each chromosome, resulting in 4 haploid cells
model the process of DNA replication using the Watson and Crick DNA model, including nucleotide composition, pairing and bonding
DNA replication is essential prior to cell division, it is controlled in cells by various enzymes and other proteins. The two strands of DNA temporarily unwind and separate to act as a template for the formation of the new strands of DNA. Nucleotides enter to form complementary base pairs with the separated strands of DNA, this creates two new strands of DNA that are identical to the original DNA.
model the process of polypeptide synthesis, including: transcription and translation
Transcription - creates messenger RNA (mRNA), using one strand of DNA as a template. The enzyme RNA polymerase is responsible for transcribing the base sequence in DNA to form mRNA. DNA can then remain protected in the nucleus, while mRNA goes out of the nucleus to the ribosomes.
Translation - mRNA binds to a ribosome, then the code that mRNA is carrying is translated by the ribosome with the help of a molecule called tRNA (transfer) which has 3 nitrogenous bases on one end and an amino acid on the other end. The ribosome processes the bases on the mRNA three at a time. These base triplets on mRNA are called codons. The ribosome matches the mRNA codons to the complementary triplet of bases (anticodons) on the tRNA molecule. This allows the ribosomes to translate the nitrogenous base code of mRNA into an amino acid chain to form a polypeptide.
assessing the importance of mRNA and tRNA in transcription and translation
tRNA - at the ribosome, the anticodon of a transfer RNA (tRNA) will temporarily bind to the complementary codon in the mRNA. This ensures that the correct sequence of amino acids from the tRNA are assembled in the polypeptide chain being formed. Each specific amino acid will only bind to a tRNA that has a matching anticodon.
mRNA - carries the code of DNA from the nucleus to the cytoplasm where it can be used in protein synthesis
Analyse the function and importance of polypeptide synthesis
Polypeptides are chains of amino acids that make up proteins which are used throughout the body to coordinate and control bodily functions. Types of proteins include, signalling eg. insulin, motor eg. actin, enzymes eg. lactase, structural eg. keratin, defensive eg. antibodies, storage eg. ferritin, transport eg. haemoglobin, sensory eg. opsins
assess how genes and environment affect phenotypic expression
Both our genotype and the environment can affect our phenotype. For example, our skin colour can be affected by several genes that control the amount and type of melanin produced. However, these genes can be stimulated to produce more melanin in response to UV rays in sunlight.
investigate the structure and functions of proteins in living things
Types of proteins include
enzymes - biological catalysts eg. lactase
signalling - allow cells to communicate with each other eg. insulin
transport - eg. haemoglobin is a protein that carries oxygen in the blood
storage - help store mineral ions in the body eg. ferritin
motor - allow movement in body eg. actin
defensive - help protect against disease- causing organism eg. antibodies
sensory - help detect stimuli in the environment eg. opsins
assess the effect of the cell replication processes on the continuity of species
Meiosis allows genetic variation which helps with the continuity of species. There are three sources of variation:
fertilisation - two parents each contribute half of the genetic material for offspring
independent assortment - meiosis randomly separates the homologous chromosomes
crossing over - a process where homologous chromosomes exchange genetic material during meiosis
Mitosis is important for growth and repair in organisms.
construct appropriate representations to model and compare the forms in which DNA exists in eukaryotes and prokaryotes
Eukaryotes store most of their DNA as multiple, non-looped chromosomes which are stored within a membrane-bound nucleus. A small portion of their DNA is also found inside the mitochondria and chloroplasts.
Prokaryotes have their DNA as a single looped, circular chromosome within the cytoplasm. Some have an additional small circle of DNA called the plasmid.
