Topic 3 - Genetics Flashcards
asexual reproduction
reproducing without fertilisation and produces genetically identical offspring
vertebrate
animal that has a backbone and a skeleton
sexual reproduction
reproducing using two parents and produces offspring its characteristics from both parents
what is DNA
contains instructions for an organism
genome
the entire set of DNA instructions found in a cell - in humans, the genome consists of 23 pairs of chromosomes located in the cell’s nucleus
chromosome
thread-like structures located inside the nucleus of animal and plant cells; each chromosome is made of protein and a single molecule of deoxyribonucleic acid (DNA) - one DNA molecule contains two strands of DNA
gene
a particular sequence of bases that codes for a protien
polymer
substances composed of smaller ‘blocks’ composed together
monomer
atoms or small molecules that bond together to form more complex structures such as polymers
diploid cell
two sets of 23 (46 in total) ‘double’
haploid
one set of 23 chromosomes ‘half’
how does meiosis happen, full explanation
division 1
- replicate DNA (add an extra arm - become x shape)
- the chromosomes line up in the centre in pairs (one chromosome from one pairs with one chromosome from dad) in random order
- cell splits in two
division 2
- chromosomes line up in the centre again, the two arms are pulled apart and pulled to separate side of the cell
- cells divide in half again
produces FOUR HAPLOID genetically DIFFERENT cells
this is how gametes (egg and sperm cell) are produced
what does meiosis produce?
produces four haploid genetically unique cells
shape of DNA
a molecule of DNA contains two strands - the two strands twist around each other and are joined together by pairs of substances called bases (complementary base pairing) to form a double helix
structure of DNA
a strand of DNA is a polymer as it’s made of lots of monomers, each monomer is called a nucleotide
structure of a nucleotide
the base is attached to a sugar and each sugar is attached to a phosphate group
what are the four bases in DNA
adenine (A), thymine (T), cytosine (C), and guanine (G)
what are the complementary base pairs
A always pairs with T
G always pairs with C
nucleotide
grouping of a base, sugar and a phosphate
what two things form the backbone of the DNA strands
sugar and the phosphate group
what does cytosine pair with
guanine
what does adenine pair with
thymine
hydrogen bond
the weak bond between the base pairs
how many hydrogen bonds does cytosine and guanine form
3
how many hydrogen bonds does adenine and thymine form
2
what contains the coded instructions for a protein
the order of bases in a gene
how do the nucleotides in a strand connect
the phosphate of one nucleotide bonds with a sugar from an other nucleotide
what’s the complementary strand of the DNA sequence: ACTGAATG
T,G,A,C,T,T,A,C
genetic code
sequence of bases causing amino acids to be joined to create a certain protein
what is the method for extracting DNA
1) grind a piece of kiwi fruit with 10ml of salt solution
2) pour that into 100ml beaker and stir for 5 minutes with 5 drops of washing up liquid
3) filter the solution into test tubes
4) add 1 drop of protease solution
5) pipette, 3-5 ml of ice, cold ethanol, slowly down the side into the test tube
- leave the tube for a few minutes a layer forms between the filtrate and the ethanol - this is DNA
how does the sequence of bases create amino acids that create a specific protein
- the bases are in blocks of 3 called triplets
- the sequence of nucleotide bases devices the sequence of amino acids
- all the amino acids (monomers) to create a protein (polymer)
what is transcription
the process of taking a single gene and making it into mRNA
what is translation
process of taking the mRNA strand and making it into a protien
what base gets replaced in mRNA
thymine gets replaced for uracil
process of transcription
- enzyme called RNA polymerase binds to a region of non-coding DNA —> the enzyme DNA helicase unzips the two DNA strands
- the enzyme then moves along one DNA strand and uses the coding DNA in the gene as a template to adds complementary RNA nucleotides
- nucleotides link to form a strand of messenger RNA (mRNA)
- once made the mRNA moves out the nucleus and attached to a ribosome
process of translation
- mRNA strand travels out the nucleus through small holes in its membrane called nuclear pores
- in the cytoplasm, the mRNA strands attach to ribosomes
- the ribosome moves along an mRNA strand 3 bases at a time (each triplet of bases is called a codon)
- at each mRNA codon, a molecule of transfer RNA (tRNA) with complementary bases lines up.
- each tRNA molecule is attached an amino acid
- as the ribosome moves along, it joins up the amino acids from the RNA molecules together, forming a polypeptide
- the polypeptide chain, and folds up to form a protein
what are the stages in protein synthesis
transcription and then translation
what’s a triplet of bases called?
a codon
mutation
a change in the bases of a gene
how can a mutation be caused
when DNA is not copied properly in cell division
phenotype
what the organism looks like
allele
different form of a gene
what are the different types of mutations
normal allele - TAC GGT TCA GAT TTC CCT TAC
single substitution allele - TAC GGT TCT GAT TTC CCT TAC —> one base changed but nothing else
single deletion mutation - TAC GGT TCG ATT TCC CTT AC —> by getting rid of 1, everything moves up by 1
single addition mutation - TAC GGT TAC AGA TTT CCC TTA —> by adding 1, everything moves down by 1
what happens when a mutation occurs in a non-coding DNA
RNA polymerase will not be able to bind and transcription will not occur
genetic variation
difference in DNA (different alleles) among individuals gives us different characteristics
homozygous
two identical versions of the same gene
heterozygous
two different versions of the same gene
gamete
a reproductive cell of an animal or plant
dominant allele
produces a dominant phenotype in individuals who have one copy of the allele
recessive allele
allele that when present with a dominant allele will not affect the individuals phenotype
genotype
alleles in an organism
how to present a dominant allele in a genetic diagram
capital letter
how to present a recessive allele in a genetic diagram
lower case letter
what sex chromosomes do females have
two X-sex chromosomes
what sex chromosomes do males have
one X, one Y and a sperm contains either X OR Y
how is gender determined
the 23rd pair of chromosomes in humans
punnet square
a table that shows possible genotypes
family pedigree chart
shows how genotypes types their resulting phenotypes are inherited in families
what are the 4 blood types
A, B, AB, O
codominance
when both alleles for a single gene affect the phenotype
3 types of red blood cell antigens on the red blood cell membrane that determine your blood group (3 ‘maker molecules’)
A, B and O
3 alleles that are responsible for the markers in the ABO system
IA IB IO
what are the phenotypes and genotypes for A, B, AB, O blood types?
phenotype: A B AB O
genotypes: IA IA IB IB IA IB IO IO
which of the following 3 alleles responsible for your type of blood is recessive to the others?
IO is recessive to both IA and IB
which blood type is a universal doner
blood type o because it doesn’t have A or B antigens so doesn’t get rejected by any immune systems and can be anywhere
sex-linked genetic disorder
disorder that show a different pattern of inheritance in men and women
which one of the human chromosomes is missing some genes
the human Y chromosome is much shorter than the human X chrormomes because it is missing some of the genes found on the X chromosome
cystic fibrosis
- genetic inherited disease
- person with CF produces large quantities of mucus in the lungs and digestive system
—> have problems with lungs and digestive system
what type of allele is cystic fibrosis found on
recessive allele and this disease will only occur when the patient is homozygous (two recessive alleles)
melanin
a protein that makes hair, eyes and skin darker in colour
e.g. a blue iris contains little melanin whereas a brown iris contains a lot of melanin
mutation
a change in a gene that creates a new allele
how does a mutation happen
when there is a mistake in copying DNA during cell division
what is the Human Genome Project
the Human Genome Project started in 1990 and was completed in 2003; hundreds of scientists from all over the world collaborated together to determine the sequence of base pairs that made up the genome of a random man and woman
how can mapping a persons genome help them
- can indicate their risk of developing diseases that are caused by different alleles of genes
- can help identify what medicines might be best to treat a persons illness
polygenetic
when a phenotype is influenced by two or more genes
e.g. eye colour, height, skin colour
how is genetic variation caused
by the different alleles inherited during sexual reproduction
how is environmental variation caused
when the individual is affected by their surroundings
e.g. how well plant grows determines on how much light, water and nutrients it gets
how is acquired characteristics caused
when a characteristic is a result of events that occur throughout their lifetime and will not be passed onto your offspring
e.g. tattoos, scars
discontinuous data
where the data can only take a limited set of values
continuous data
where the data can be any value at any range
example of continuous data
height, weight, temperature, length
example of discontinuous data
person’s blood group, gender
possible mechanisms for variation in an organism:
- genetic
- environment
- acquired characteristics
why is ice cold ethanol added in the DNA extraction practical
to precipitate (see) the DNA because DNA is insoluable in ethanol
Why do you have to grind fruit in DNA extraction?
breaks the cell membrane, releasing the DNA
how can a mutation in the NON-CODING region of a gene lead to the production of less protein
RNA polymerase doesn’t bind as well so the amount of mRNA that is produced is altered
