Genetics Flashcards
What are chromosomes?
Long molecules of DNA inside a nucleus.
23 pairs inside the nucleus of body cells.
What is DNA?
DeoxyriboNucleic Acid. It is a chemical that all genetic material in a cell is made from. It is a polymer. It is made up of two strands coiled together as a double helix.
What is the structure of DNA?
DNA strands are polymers made up of repeating nucleotides.
Each nucleotide is made up of one sugar (deoxyribose) and a phosphate.
The sugar phosphate molecules form the backbone to the DNA stands. One of the four bases ACTG joins to the sugar molecule.
How do the bases pair in DNA?
A-T and G-C
How many bases code for an amino acid?
Three/triplets
What is a gene?
Small section of DNA found on a chromosome
Genes tell cells in what order/sequence to put amino acids in to make specific protein.
How are proteins synthesised?
DNA unwinds exposing one strand.
An mRNA copy is made using the DNA as a template.
U replaces T.
The first stage happens in the nucleus.
mRNA is single stranded and can leave through the DNA pore.
Proteins are made in the cytoplasm.
The ribosome reads the mRNA . Every three bases codes for an amino acid.
The correct amino acids are brought to the ribosome by carrier molecules. tRNA. This stage is called translation.
What do genes code for?
A particular sequence of AMINO ACIDS put together to make SPECIFIC PROTEINS
What is a genome ?
The entire set of genetic material in an organism
Why is it important to understand the human genome? (3)
1)Allows scientists to IDENTIFY GENES that link to different types of disease i.e Down Syndrome
2)Development of effective treatments
3)Can be used to trace migration of certain populations by tiny differences in GENOMES.
How many chromosomes are in a normal body cell?
46 or 23 pairs
How many chromosomes in a gamete (sex cell)?
23
Give 3 details of sexual reproduction in plants/animals
-Animal gametes -egg & sperm
- Plant gametes-ovule & pollen
-Each gamete contains 23 chromosomes
-nucleus of both gametes fuses=mixture of genetic info=variation in offspring
Give 3 details of Asexual reproduction
-One parent
-Genetically identical offspring-clone
-Happens by mitosis
Give 2 examples of organisms that reproduce asexually
Bacteria
Some animals & plants
What type of cell division are gametes (sex cells) produced by?
Meiosis
What are the 5 stages of Meiosis
1 - Duplicate genetic info-forming ‘X’ chromosomes that arrange themselves into pairs
2 - Chromosomes line up in centre of cell in homologous pairs
3 - Pairs pulled apart so each new cell only has one copy of each chromosome-some of the father’s chromosomes and some of the mother’s go into each cell randomly, but each cell has an equal amount of chromosomes in total
4 - 2nd division-chromosomes line up in centre & separated again
5 - 4 gametes-each with single set of chromosomes
Give 2 details about the 4 gametes produced in meiosis
1 - Each contain 1 set of chromosomes
2-Each gamete genetically different
Why are gametes produced in meiosis genetically different?
Because chromosomes are shuffled up during meiosis and each gamete only gets half of them at random
Explain how/why the cell produced by gamete fusion replicates itself (3)
1) After 2 gametes fused during fertilisation-resulting new cell divides by mitosis to make copy of itself
How many pairs of chromosomes are in a human body cell?
23 Pairs
What do each of the chromosomes control?
22 pairs of chromosomes are matched/homologous pairs-control CHARACTERISTICS
What are the male and female chromosomes?
Males: XY-The Y chromosome causes male characteristics
Explain the chances of a child being male/female using a punnet diagram.
50% chance of male and 50% chance of female.
