inheritance and reproduction Flashcards
eg DNA, genes, punnet squares, protein synthesis
Where are genetic materials stored in a cell?
The nucleus
A chromosome is
Long lengths of DNA coiled up
A gene is
A short section of DNA
A DNA is in the shape of a
Double helix
There can be different versions of the same gene, which give different versions of a characteristics, such as green or brown eyes. What are these called?
Alleles
Complementary base pairs in DNA are:
A and T (adenine and thymine)
C and G (cytosine and guanine)
Each gene in DNA codes for a protein, meaning that they decide our ——-
characteristics
What is mitosis?
A cell reproduces itself by splitting to form two cells with identical sets of chromosomes
Meiosis produces…
four haploid cells whose chromosomes are not identical
Asexual reproduction uses which process?
Mitosis
Gametes are produced in which process?
Meiosis
Protein synthesis has two stages
Transcription and translation
Translation is:
(In simple terms)
Using the mRNA strand to make a protein
Transcription is:
(In simple terms)
A single gene is taken and copied into mRNA
mRNA uses a different base - what is the base that has been removed and what has it been replaced with?
REMOVED: thymine - T
REPLACED WITH: uracil - U
mRNA stands for -
messanger RNA
tRNA stands for -
transfer RNA
Genetic variation definition
Is the difference in DNA sequences of individuals within the same species caused by mutations
Meaning of evolution
A change in the inherited characteristics of a population over time through a process of natural selection which may result in the formation of a new species
Why are bases important?
They code for amino acids which form the protein
mRNA makes a copy of DNA to take to the…
Ribosome
The process of transcription (in steps)
- RNA polymerase binds to the DNA just before the gene begins
- the two strands of DNA separate after the RNA polymerase so the bases are exposed
- the RNA polymerase will read the strand of DNA’s bases and make a mRNA strand using the complementary bases (G to C, A to U)
- the DNA then closes after the RNA polymerase has moved onto the next base, and opens at the front so it can read the next one so less DNA is exposed
- RNA polymerase detaches and DNA closes
- mRNA can now leave the nucleus and go to the ribosome
What is used to make mRNA?
Part of DNA - template strand
The reader - RNA polymerase
The process of translation (in steps):
- tRNA have an amino acid at the top and an anti codon at the bottom and will be attracted to the corresponding triplet
- the ribosome then joins the amino acids at the top of the two tRNAs that have been coded for
- it moves along the mRNA and does it to the next codon
- the first tRNA detaches, but leaves the amino acid, so the tRNA is able to join the 2nd and 3rd tRNAs
- this forms a chain of amino acids after being repeated again and again
- the chain then folds up and becomes a protein
The codons (three bases) code for:
Amino acids/proteins
Where does transcription take place?
The nucleus
Where does translation take place?
The ribosome
How is mRNA different to DNA?
It is single stranded and shorter
A chain of amino acids is called a
Polypeptide
What is a gamete?
An organisms reproductive cell that has half the number of chromosomes
Heterozygous
When one of the inherited alleles is dominant and the other is recessive
Dominant allele
Only one out of the two alleles is needed for it to be expressed and for the corresponding phenotype to be observed
Two copies are needed for it to be expressed in the phenotype
Recessive allele
Homozygous
When both inherited alleles are the same (eg two dominant or recessive alleles)
Codominance
When neither allele is dominant so both contribute to the phenotype
What is variation?
It is the difference in DNA sequences of individuals within the same species
What influences variation?
- GENETIC FACTORS - dependent on alleles
eg eye colour or blood type - ENVIRONMENTAL FACTORS - it is caused by differences in lifestyle, diet and climate which could lead to organisms adapting
- GENETICS AND ENVIRONMENTAL FACTORS eg height - some is genetic and some is food
Variation occurs in meiosis because
Random fertilisation increases genetic variation as the fusing of sperm and egg are random
Gametes have random chromosomes so this increases variation
—> siblings do not have the same genes despite having the same parents
what are the names of the bases in DNA
adenine - thiamine
cytosine - guanine
—> thiamine becomes uracil
