P2 CODOMINANCE + higher 3b genetics / inheritance Flashcards
what is a gene?
A gene is a small section of DNA on a chromosome that codes for a particular sequence of amino acids
what is a genome?
A genome is hereditary information encoded in DNA.
what is found in the nucleus?
nucleus of a cell contains chromosomes
where are genes located?
in the chromosomes
what is the structure of a DNA molecule?
- there are bases (which pair up), AT and CG
- these make up the shape and are the “backbone” of it
- it is a double helix structure
what are nucleotides?
the basic units of DNA
what do nucleotides consist of?
deoxyribose sugar, phosphate and a base
what is an allele?
different versions of the same gene (like eye colour)
what is the purpose of an allele?
to give differences in inherited characteristics
what is protein synthesis?
the process in which cells make proteins from DNA
how does protein synthesis work?
mRNA, a copy of DNA moves from the nucleus into the ribosomes. proteins are synthesised in the cytoplasm. they are then folded into a specific shape which makes a protein for a job. protein synthesis happens in two stages transcription and translation.
what is mRNA?
messenger RNA
what happens in the transcription process?
- DNA unwinds and the hydrogen bonds break
- exposes the gene to be transcribed
- a complimentary copy of the code from the gene is made, mRNA
- it then leaves the nucleus via a pore
- code it is read in threes
what happens in the translation process?
- the mRNA attaches to a ribosome
- in the cytoplasm there are tRNA, which have a triplet of unpaired bases at one end, and an area where a amino acid can attach itself
- the tRNA molecules bind with specific amino acids and bring them to the mRNA on the ribosome
- the anticodon pairs with a codon
- this process continues until a stop codon is reached
- this is where the amino acid is complete forming a polypeptide
what happens if there is a wrong code? (didnt read the right base in one stage)
Each triplet codes for one amino acid, if one letter is changed the whole structure of the protein is changed and causes defects
what are the three types of mutations that happen when the codes are being read?
Substitution, not that harmful
○ Not coding the right letter, so another letter takes its place
○ Doesn’t change the triplets and only effects one protein code
Deletion, can be very harmful
○ Misses a letter, so it deletes a part of a triplet
○ Changes every triplet after that so it can be very harmful, none of the protein codes would be the same
Addition, can be very harmful
○ Opposite of deletion, has the same effect.
what does dominant allele mean?
only one copy of the dominant allele is needed for it to be expressed
what does recessive allele mean?
you have to have two recessive alleles for it to be expressed, it is only expressed if there is no dominant alleles present.
what does homozygous mean?
you have two of the same allele
what does heterozygous mean?
you have two different alleles for one thing
what is a homologous pair?
Every chromosome has matching pairs, one from mum and one from dad
what can also cause mutation?
radiation, things you ingest i.e cigarettes
what two things effect the appearance of an organism?
- Genes (inherited characteristics)
2. The effects of the environment in which is lives
what is a phenotype?
Observable characteristics of an organism
what is a genotype?
The combination of alleles an organism
what is meant by co-dominance and what is an example?
condition where both alleles are expressed in the phenotype
- an empale is when flowers have a red allele and a white allele and the flower produced is pink
how do you identify co-dominance in punnet squares?
we use the subscript of the first letter of the colour (carrying on from the example)
Cr - is a red flower
Cw - is a white flower
- for a fully red flower the genotype would be CrCr
- A fully white flower the genotype would be CwCw
- CwCr would mean the flower is pink
what is a polygenic trait?
Height is controlled by many genes, so there is a scale and it is therefore a continuous type of data. Height is something effected by both genes and environment, all polygenic traits are effected by both
an example of monohybrid inheritance
blood, there are certain blood groups and you can only get certain ones with the alleles. and it is controlled by a single gene
how is the sex of a person determined?
XX female
XY male
females only carry XX and males carry one or the other
diploid and haploid number of chromosomes in human cells?
46 is diploid
23 is haploid
what is the process of evolution by means of natural selection?
the more advantages traits are the ones that better adapt and will survive and reproduce. the favourable traits are passed through generations.
what is a genetic diagram?
the one that takes longer and is bigger than a punnet square, the one with all the lines
sex linked traits?
a sex linked trait is the trait that is carried on only through the X chromosome
why can’t the father XY pass down a sex liked characteristic to their sons XY?
because the father can only pass down a Y chromosomes to their son, and the Y chromosome doesn’t carry and sex linked traits
how do you write sex linked traits?
the X and Y with a subscript of the first letter of the trait.
what is mitosis?
mitosis makes genetics identical cells, they make somatic cells
this type of cell division can be found everywhere
mitosis creates diploid cells
what is meiosis?
is exclusively for gametes, sex cells, theses happen in only specific cells. This creates genetically unique cells. meiosis creates haploid cells
how does genetic mutation cause faulty enzyme function?
it might alter the shape of the protein if there is a piece of genetic code missing, and the substrate might not fit properly and therefore will not function as an enzyme.
difference between mitosis and meiosis?
mitosis
- 2 daughter cells produced
- Happens everywhere in the body
- Produces genetically identical cells, somatic
- Diploid cells
- Cells divide once
meiosis
- 4 daughter cells produced
- Happens only in sex gametes
- Genetically varied cells
- Haploid cells
- Creates variation
- Cells divide twice
- Chromosomes are rearranged
how is code read?
- code it is read in threes
where does transcription happen?
nucleus of the cell
where does translation take place?
cytoplasm and the ribosomes
what is a codon?
the complementary triplet of code, mRNA
what is a anticodon?
the triplet of unpaired bases, tRNA
what are other types of RNA?
transfer RNA, tRNA, ribosomal RNA, rRNA, and messenger RNA, mRNA
what is different about RNA, compared to DNA?
- RNA is single stranded
- RNA contains uracil instead of thymine
