Variation, Genetics and Inheritance Flashcards
What is a mutation
A random change in an organisms DNA
What does DNA stand for
Deoxyribonucleic acid
What shape are DNA strands
double helix
What is a gene
a small section of DNA found on a chromosome
Define genome
A geneome is an entire set of genetic material in an organism
Where in a cell is DNA found
nucleus
How does a gene help a cell to make a specific protein
each gene codes for a particular sequence of amino acids which are put together to make a specific protein
What 3 things does a nucleotide consist of
sugar, phospate and a base
what are the 4 different bases
A,T,C,G
Which bases pair with eachother
A+T G+C
Give one function of non-coding parts of DNA
they control whether or not a gene is expressed
Where are proteins assembled
Made in the ribosomes
What happens when a protein chain is complete
It folds into a unique shape which allows the protein to perform a task its meant to do.
Function of enzymes
used as a catalyst to speed up chemical reactions in the body
Function of hormones
used to carry messages around the body
What do carrier molecules do
Bring the correct amino acids to the ribosomes in the correct order
do mutations occur continuously
yes
What do mutations do
change the sequence of DNA bases in a gene, which produces a different form of the gene.
What are the 3 types of mutation
Insertions
Deletions
Substitutions
Explain Insertion mutations
where a new base is inserted into the DNA base sequence where it shouldn’t be.
Explain Deletion mutations
When a random base is deleted from the DNA base sequence.
Explain substitution mutations
when a random base in the DNA base sequence is changed to a different base
Define sexual reproduction
where genetic information from two organisms (mother and father) is combined to produce offspring which are genetically different to either parent,
How many chromosomes does a human gamete contain
23
What are the male and female gametes
MALE- sperm cell
FEMALE- egg cell
What is fertilisation
the fusion of gametes
Expalain fertlisation in humans
The egg cell (from the mother) and the sperm cell (from the father) fuse together to form a cell with the full number of chromosomes (46)
Why are the parents offspring genetically different
because there are two parents, the offspring contain a mixture of their parents’ genes
Briefly explain asexual reproduction
In asexual roproduction there is only one parent. There is no fusion of gametes, no mixing of chromosomes and no genetic variation between plant and offspring meaning that the offspring are genetically identical to the parent.
What are the 5 steps of meiosis
- Cell duplicates its genetic information forming two chromosomes
- In the first division in meiosis the chromosome pairs line up in the center of the cell
- The pairs are then pulled apart so each new cell has one copy of each chromosome.
- In the second division, the chromosomes line up again in the centre of the cell. They are then pulled apart
- You then get 4 gametes, each with a single set of chromosomes in it.
How many chromosomes are in a human cell
46
advantage of sexual reproduction
Variation in the offspring increases chances of surviving a chaange in the environment
advantage of asexual reproduction
One parent so uses less energy and is faster
What chromosomes do males have
X AND Y
What chromosomes do females have
two X chromosomes
Define allele
Different forms of a single gene
Define recessive
The allele that only has an effect when the genotype is homozygous
Define dominant
The allele that has an effect in either homozygous or heterozygous state
Define genotype
the genes an organism contains
Define phenotype
an organisms appearence or characteristic
Define homozygous
Having two identical alleles for a particular gene
Define heterozyggous
having two different alleles for a particular gene
What is cystic fibrosis
an inherited disorder of the cell membranes, whch results in the body producing lots of mucus in the air passages and in the pancreas
What are the symptoms of cystic fibrosis
difficulty breathing
Is cystic fibrosis carried by a dominant or recessive allele
recessive
What is polydactyly
An inherited disorder where a baby is born with an extra digit
Is polydactyly carried by a dominant or recessive allele
dominant- if one parent has that allele it can be inherited
What is embryonic screening
A way of detecting inherited disorders such as cystic fibrosis in embryos.
What are the two different ways of embryo screening
PGD (pre implantation genetic diagnosis) CVS (Chorionic villius sampling)
Explain PGD
During IVF, embryos are fertilised in a lab and then implanted into the mothers womb. Befoore being implanted, its possible to remove a cell from the embryo to analyse genes. Embryos with healthy alleles will be implanted into the mother and embryos with unhealthy alleles will be destroyed.
Explain CVS
CVS is usually carried out between 10 and 13 weeks of pregnancy. It involves taking a sample of cells from part of the placenta and analysing their genes. If the embryo is found to have an inherited disorder, the parents can decide if they want to terminate the pregnancy
3 Arguments for embryonic screening
- Helps to stop people suffering from inherited disorders.
-Treating disorders costs lots of money, so screening the embryos could reduce healthcare costs
-Gives parents a choice if they want to terminate a pregnancy
3 Arguments against embryonic screening
- May become a point where everyone wants to screen their embryos so they can pick the most desireable one.
-Expensive
-There is a risk that CVS could cause a miscarriage
Examples of genetic variation
Eye colour
Blood group
Flower colour
Examples of environmental variation
Weight
Accent
Examples of environmental and genetic variation
Height
Intelligence
Health
