Unti 3 - Genetics Flashcards
What is sexual reproduction?
The reproduction of an organism involving the ale sex cell fertilising the female sex cell.
What is asexual reproduction?
The reproduction of an organism which doesn’t involve fertilisation.
What does asexual reproduction involve?
A clone, genetically identical to the parent.
Is asexual common in vertebrates or invertebrates?
Invertebrates
What re runners in a plant?
Special stems that grow out from the adult plant.
What does a runner allow the plant to do?
The daughter plant can grow further away from the parent whilst still being attached so it can get the nutrients and water.
What happens by a node in a runner?
A new plant starts growing.
Why in sexual reproduction is the offspring always different?
It combines characteristics from both parents.
Give examples of how variation can be beneficial
If the environmental conditions like temperature or different diseases occur, some of the variations should be able to survive.
Why is asexual reproduction much faster?
There is no need to find a mate.
When is asexual reproduction the most advantageous?
When there is a lot of resources like food available.
What is a Zygote?
A single fertilised egg cell
What is fertilisation?
When two gametes fuse
What is a gamete?
A sex cell e.g egg or sperm
What is mitosis?
A type of cell division
Name the stages of mitosis
(prophase), interphase, metaphase, anaphase, telophase, cytokinesis.
What is DNA
The coding found in a molecule with the instructions for the organism.
What is a genome
The DNA of an organism
How many molecules of DNA is a human genome?
46
What are genes?
Sections that contain code for making a protein found along the DNA
How is a protein made?
A chain of amino acids linked together.
Around how many genes do humans have?
20,000
How many chromosomes does a human body cell contain?
2 sets of 23
Why do gametes only need 1 set of chromosomes?
When it is fused in fertilisation, there would be 2 sets of chromosomes instead of 4.
What does 2n and 1n mean?
Diploid and haploid cells
What does mitosis produce?
2 diploid daughter cells
What does meiosis produce?
4 haploid daughter cells
What process if used to produce gametes?
Meiosis
Explain the process of meiosis
Each of the 4 chromosomes duplicate, the 2 sets stay attached forming Xs, the cell then splits into two containing 2 pairs each, each cell then splits again into two this time also splitting the pairs of chromosomes.
How are chromosomes formed?
One long DNA molecule is tightly coiled and held together by the proteins.
What is the formation of a DNA molecule?
Two strands form a shape called a helix (coil) which are held together by bases to form a double helix.
What are the complementary base pairs?
A & T
C & G
What is a nucleotide
The group of a base attached to a sugar which is attached to a phosphate group.
Why is DNA a polymer?
It is made of many similar units joined in a chain.
What is the hydrogen bond?
A weak force of attraction between the bases.
Why can only certain bases pair?
They have slight electrical charges which only attract a certain base.
What impact does the order of the bases have?
It contains the coded instructions for a protein.
Why does everyone except identical twins have a different DNA?
The order of the bases slightly change
Give an advantage of DNA extraction
They can identify what a substance is through the order of the bases.
Give a method of extracting DNA.
Dissolve salt (clumps DNA) in water and add washing up liquid (breaks down cell membrane and membrane around nucleus). Add to mashed substance. Put in 60 degrees water bath and filter mixture. Put filtrate into beaker and add protease enzyme solution (breaks down proteins). Slowly add ethanol, DNA is insoluble in this so it forms a precipitate. A white layer forms between the filtrate and ethanol.
Who were the first people to work out the structure of DNA?
James Watson and Francis Crick
What is the first stage of protein synthesis?
Transcription
What happens is transcription?
The DNA bases are used to make a strand of RNA.
What is gene expression?
The process of the DNA information being copied so it can be transferred into the cytoplasm.
What is messenger RNA?
A polymer made from nucleotides, like DNA but shorter and only one strand
Describe the process of transcription.
An enzyme called RNA polymerase attaches to the non-coding part of DNA. The DNA strands unzip and the RNA moves along one strand and uses it as a template to make mRNA. When mRNA is made, it moves out of the nucleus and joins a ribosome
What happens after transcription?
Translation
How does the mRNA strand travel out of the nucleus?
It goes through the nuclear pores, tiny holes in the nucleus membrane.
What happens to the mRNA strand once it is in the cytoplasm?
It attaches to ribosomes
Describe the process of translation.
Once the mRNA has bound to the ribosome, amino acids are brought over by the enzyme, tRNA. The order that the amino acids are brought over match the codons. The anticodons ensure that the amino acids are brought over in the right order. The amino acids are then joined by the ribosome and makes a polypeptide (protein)