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)
What creates a genetic variation/ mutation?
Change in the bases
What causes mutations? (4 things)
The DNA not being copied correctly. Environmental factors. A change in order of bases. The two sets of genes having the same alleles.
What is a phenotype?
An observable characteristic.
What is an allele
The different formations of a gene. E.g gene is height, alleles are tall and short.
How are your characteristics formed?
The alleles you inherit.
What are the two kinds of polypeptides in Haemoglobin?
a and b thing
How does a protein form from Haemoglobin?
The polypeptides fold and join to make a spherical shape.
How is sickle cell disease formed?
The polypeptides fold incorrectly so the protein doesn’t function properly. This results in the red blood cells sticking together causing episodes of extreme pain.
What is a genetic disorder?
A disorder caused by mutations of a gene.
What happens in mutations in non coding DNA?
The RNA polymerase attaches to DNA bases. If the binding does not work well which reduces transcription, a mutation can occur.
What did scientists used to think variations were?
A blend of the parents
What did Mendel use for his experiments?
Pea plants
How did Mendel breed the plants?
He used a paintbrush to move the pollen with the male gametes to another plant.
What did Mendel conclude to that controlled the variation characteristics?
Inherited factors
If the plant self-pollinated, what would the variation be of the offspring to the parent?
They would be the same
Give models three laws of inheritance
Each gamete only receives one allele for a gene.
The allele received is random and doesn’t depend on any other alleles.
Some alleles of a gene are more powerful which always has an effect on the offspring
Why did scientists ignore Mendels theory?
If the factors couldn’t change, a species could not evolve
Rank in order of size largest first: chromosome, base, gene, genome
Genome (all the chromosomes together), chromosome, gene, base
Why does a body cell contain two sets of each gene?
It contains two sets of each chromosome
What does homozygous mean
When the alleles for a gene are the same
What does heterozygous mean
When the alleles for a gene are different
Why do gametes only contain one copy of each gene?
They only have open copy of chromosomes
What does dominant and recessive allele mean?
Dominant is when the allele has an effect on the phenotype
Recessive is when it doesn’t have an effect on the phenotype
When is a recessive characteristic seen?
When both alleles are recessive
What does monohybrid inheritance mean?
The study of inheritance for one characteristic
How is the dominant and recessive allele shown in a diagram?
Dominant is capital letter
Recessive is lower case letter
What is the genotype.
The alleles in an organism
What is a phenotype?
What the organism looks like.
What are the two types of your sex schromosomes?
X and Y
What are the genotypes t males and females
Males is X and Y
Females is X and X
What are the genotypes for the egg and sperm cell
Egg is always X
Sperm is either X or Y
What is the probability
The likelihood of something happening
What happens if someone is given the wrong blood type?
The red blood cells can stick together in a lump which can kill.
What are the 4 groups of blood?
A, B, AB, O
What determines your blood group?
The marker molecules on the outside of your red blood cells.
What are the three types of marker molecules?
A, B and O
How are the genes for the red blood cells written?
I(A) I(B) I(o)
Why can people be homozygous or heterozygous for the gene of red blood cells?
There are two copies of the gene
Which alleles for red blood cells are recessive and dominant?
I(A) and I(B) are dominant
I(o) is recessive
What are codominant alleles?
When both are dominant
Why are men more likely to develop a disorder?
The X chromosome is longer than the Y chromosome. If part of the X chromosome carries a disorder that the Y chromosome doesn’t have as it is shorter, the man will develop the disorder.
Why may women not develop disorders
As both of the X chromosome have the same amounts of genes, it one carries the disorder but is recessive and the other doesn’t and is dominant, the women won’t develop the disorder.
What are sex-linked genetic disorders?
When disorders show a different pattern of inheritance in men and women.
Give an example of a sex-linked genetic disorder.
Red-green colour blindness.
What is a carrier?
When the women carries a disorder that is recessive so doesn’t take any effect.
What is the gene that causes most variation in eye colour?
OCA2
What is melanin?
A protein that adds pigment as it is dark coloured
What is a mutation?
A change in a gene that creates a new allele
When are mutations more likely to happen?
When the DNA is damaged by radiation or certain substances.
Why do mutations not always affect the protein?
They can happen in small parts of a gene so may not take effect.
What does The Human Genome Project do?
They map out parts of the human genome and show the different sequences of the bases.
What has The Human Genome Project discovered?
That over 99% of the bases are the same for everyone.
Give two advantages of The Human Genome Project mapping a Genome
It indicates the risk of developing a disease. It helps to identify which medicines are best to treat the disease.
Why do some medicines not work for people?
The different alleles can affect how it works.
How is genetic variation caused?
The different alleles being inherited during sexual reproduction
Give an example of environmental variation
A plant not growing well due to deficient light, water and nutrients
What are acquired characteristics?
Characteristics that are changed during the life of the individual. E.g loss of limb
What are the 2 types of variation?
Continuous and discontinuous.
What is discontinuous variation and an example
The data can only take a limited set of values. E.g number of whole leaves as you can’t have in between values as they have to be whole.
What is continuous variation and an example
Where the data can be any value in a range. E.g length of leaves.
What is different in bar charts for discontinuous and continuous data?
Discontinuous data has a gap between the bars but continuous doesn’t.
What is normal distribution.
When the continuous data forms a bell shape.
Why does continuous data form a bell shape?
It is what is expected for large amounts of data. The most common is the middle value in the range. The further from the middle, the less frequent.
What is DNA made up of
Nucleotides
What are the bases in a double helix joined together by
Weak hydrogen bonds
What is DNA made up of
Nucleotides
What are the bases in a double helix joined together by
Weak hydrogen bonds
What is a gene
A section of DNA on a chromosome that codes for a particular protein
What is the genome
All the DNA
What makes proteins different?
Their own particular number and order of amino acids
What decides the order of amino acids in a protein
The order of the bases (the DNA codes for the protein)
What are non-coding regions of DNA
Regions that don’t code for any amino acids
What is the purpose of transcription
To make mRNA from RNA polymerase and DNA.
What different base is used in mRNA than DNA
U instead of T
What is the difference between a codon and a base triplet
A codon is the name for a bad triplet only in mRNA
