B13 Flashcards
What are the two ways of reproduction?
Sexual reproduction and asexual reproduction.
What is asexual reproduction?
It involves one parent where the cells divide by mitosis. There is not variation in offspring and gives rise to genetically identical offspring. Happens in cells and some plants.
What is sexual reproduction?
It is where a male and female gamete fuse together to form a zygote, which develops into a new individual. There is a mixing of genetic information which leads to variation in the offspring.
What is meiosis?
It happens in the ovaries or the testes depending on your gender. When a cell divides to form gametes the genetic information is copied so there are four sets of each chromosome instead of the usual two sets. The cell then divides in quick succession to form four gametes, each with a single set of chromosomes.
What is fertalisation?
It is adding variation, when two sex cells join, forming a single new cell with a full set of chromosomes. When this happens, this new cell begins to divide by mitosis to form a new individual.
What is natural selection?
This is where your variation gives either an advantage or a disadvantage to an environment change, giving some a survival advantage so they can reproduce.
How does a fungi reproduce?
Asexually, where the spores are produced by mitosis so are genetically identical to their parents given out to the environment.
How does a plant reproduce?
Sexually, where the gametes are produced using meiosis and are the pollen and the egg cells. The pollen must reach a female part of another flower called pollination, fusing with the egg cell and creating seeds.
How does a parasite reproduce?
They reproduce asexually, e.g. malaria in the human liver and blood cells.
What is DNA?
A long polymer that it in a double helix structure. The genes are small sections of this DNA where your genetic information is stored. Each gene in your chromosomes codes for a particular sequence of amino acids to make a specific protein.
What is the human genome?
It is the entire genetic material of the organism which includes all chromosomes found in the mitochondria again.
Why does the human genome matter?
It has helped us understand inherited disorders and can have chance to over come them through medicines or by repairing the faulty genes.
What are the long strands of DNA made of?
They are made of alternating sugar and phosphate sections. Attached to each sugar is a base represented by A, C, G, T with C and G being a pair and T and A being a pair. This combination is called a nucleotide.
How does protein synthesis occur in DNA?
Genes in the DNA produce a template for the protein, which reflects the sequence of bases in the DNA but is small enough to leave the nucleus through pores in the membrane. It then binds onto the surface of the ribosome. The cytoplasm contains carrier molecules, each attached to a specific amino acid. They are joined to form a specific protein. The carrier molecules keep bringing specific amino acids to add to the growing protein chain and then the protein detaches from the carrier molecules and the carrier molecules detach from the template and return to the cytoplasm to get more amino acids.
What is gene expression?
When a gene codes for a protein that is synthesised in the cell, the gene is said to be expressed. However there is non-coding parts of our DNA which can turn genes on or off so variations in these areas can affect gene expression. This in turn affects the phenotype which is the physical appearance of an organism.
What is mutation?
It is where new genes form from changes in existing genes and these changes are what is known as mutations. They do not alter the protein or they alter it so slightly that the function is not affected.
What are alleles?
These are different forms of gene which code for different proteins.
What is a homozygote?
An individual with two identical alleles for a characteristic.
What is a heterozygote?
The individual with different alleles for a characteristic.
What is a genotype?
This describes the alleles present or genetic makeup of an individual regarding a particular characteristic.
What is a phenotype?
This describes the physical appearance of an individual regarding a particular characteristic.
What is a dominant and a recessive allele?
A dominant allele is always expressed in the phenotype, even if only one copy is present. A recessive allele is only expressed if two copier are present.
What is polydactyly?
It is where babies are born with extra fingers or toes, which is caused by a dominant allele.
What is cystic fibrosis?
A genetic disorder that affects many organs of the body, particularly the lung. It is where your mucus made by cells in many areas of the body becomes very thick and sticky, clogging organs. It is a recessive phenotype and is caused by recessive alleles which must be inherited form both parents.
What are the two methods that can screen an embreyo?
You would do this through amniocentesis which involves taking fluid around the developing fetus, containing cells that can be checked for genetic screening. Or you can do chorionic villus sampling of embryonic cells which is done by taking a small sample of tissue providing fetal cells to screen.
Why would you screen an embryo but why is it not ethical?
This is to identify genetic disorders but it can be unethical due to some parents wishing to terminate the pregnancy if problems do arise.
