Genetics Flashcards
Describe 2 advantages of asexual reproduction
- Requires 1 parent (No need to find a mate)
- Offspring can be produced very quickly due to the reproductive cycle
Explain a disadvantage of asexual reproduction
No genetic variation, meaning if environmental conditions become unfavourable, the whole population may be affected, less chance of survival.
Explain an advantage of sexual reproduction
Introduces genetic variation into the population, meaning if there was an environmental change, some species would have more chance of survival.
Describe 2 disadvantages of sexual reproduction
- Takes long periods of time, less offspring can be produced
- Two parents needed, can be a problem for isolated individuals
Describe the cells produced by meiosis.
Produces 4 genetically different daughter cells, called gametes. They are haploid cells (Half genetic material).
Why are haploid cells produced via meiosis.
So when they fuse with another gamete (sex cell), the cell will have the full genetic material of a normal cell.
Describe the structure of DNA
They are polymers made up of nucleotides (A sugar, phosphate and base). Two strands of DNA are coiled into a double-helix shape.
How are DNA strands held together to form a double helix shape
The strands are linked by a series of complementary base pairs
joined together by weak hydrogen bonds
Describe the word Genome
The entire DNA of an organism
Describe the word Gene
A section of DNA which codes for a protein
Explain the stage of protein synthesis, Transcription
RNA polymerase binds to non-coding DNA located in
front of a gene.
Double helix structure of DNA uncoils leaving exposed bases.
RNA polymerase produces a complementary mRNA
strand from the coding DNA of the gene.
mRNA leaves to enter cytoplasm via a nuclear pore.
Explain the stage of protein synthesis, Translation
mRNA attaches to a ribosome.
Each three bases in the mRNA is a codon, 1 codon codes for 1 amino acid. tRNA brings amino acid the the mRNA, along with anti-codons to compliment the codons on the mRNA. Chain of amino acids form, known as a polypeptide. The tRNA detaches, and the polypeptide chain folds up, forming a protein
Define the terms: A) Chromosome
B) Allele
A) Chromosomes in the nucleus are made from genes which are made from DNA
B)Alleles are different versions of the same gene
Define the terms: A) Dominant
B) Recessive
A) An allele which is always present (Shown) even if only one copy is present.
B) Only expressed if the individual has two copies and does not have the dominant allele of that gene
Define the terms: A) Homozygous
B) Heterozygous
A) Homozygous alleles are both identical for the same characteristic, for example AA or aa.
B) Heterozygous alleles is when an individual has different alleles for a particular gene.
Define the terms: A) Genotype
B) Phenotype
A) An organisms complete set of genetic material
B)The visible characteristics in an individual resulting from the expression of genes
Define the terms: A) Gamete
B) Zygote
A) A haploid sex cell produced by meiosis
B) Formed by the fusion of two gametes
Explain the practical for extracting DNA from fruit (6)
- Mash some strawberries, put them in a beaker with a solution of detergent and salt.
- The detergent will break down the cell membranes to release dna.
- Filter the mixture to get the froth and insoluble bits of the cell out.
- Slowly add some ice cold alcohol.
- The dna will come out of the solution, it is not soluble in cold alcohol. It will appear as a stringy white precipitate.
- Fish it out with a glass rod.
Why does the order of bases matter in the translation stage of protein synthesis
Each codon, 3 bases, codes for a specific protein, that has a particular job. The body would not function efficiently if we did not have ordered codons
Describe how genetic variants in the non coding region of dna can affect the phenotype of a person
May give a person different alleles, as a different protein is coded for, giving them different visible characteristics (such as brown instead of black hair). These are known as mutations.
Give 1 reason why it was difficult for people to fully understand Mendel’s work at the time of discovery
Scientists didn’t have the background knowledge to fully understand his findings. They had no idea about genes and DNA.
Explain why humans have differences in their inherited characteristics due to alleles
Some alleles are dominant, and some are recessive. Different one’s are shown for every person. Every person has a different genome (the makeup of our alleles), hence our differing characteristics.
What do genetic diagrams, punnet squares and family pedigrees show
The chance an offspring has of a certain characteristics
Describe how the sex of offspring is determined at fertilisation
If a female receives the y chromosome from the male, offspring will be male. If a female receives the x chromosome, offspring will be female.
Which blood group shows co-dominance and why
AB, both alleles are dominant, so both are expressed at the same time
Which blood group is the:
A) Universal donor
B) Universal recipient
A) O
B) AB
Alleles for blood types A and B are always dominant. State the only way someone can inherit blood type O.
Offspring receives the blood type O allele from both parents.
Explain how you can inherit a sex linked genetic disorder
Passed down from parents on either the X or Y chromosomes.
Why are males more likely to develop sex linked genetic disorders than females
Males only have one Y chromosome, meaning they often only have one allele for sex linked genes. Because males only have one, even if the allele is recessive it will be shown
How is most of your phenotype presented
as a result of multiple genes rather than single gene inheritance
Describe 2 causes of variation that influence one’s phenotype
- genetic variation – different characteristics as a result of mutation and sexual reproduction
- environmental variation – different characteristics caused by an organism’s environment (acquired characteristics)
Is there much genetic variation amongst a population. If so, state why
there is usually extensive genetic variation within a
population of a species and these arise through mutations
Why may some genetic mutations not change one’s phenotype
The mutation may still code for the same protein, causing no difference
Genetic mutations may have 3 effects. State each
No effect, benefit, disadvantage
Describe the outcomes of the human genome project
20500 genes have been located
1800 genes related to disease have been found
Describe potential applications of the human genome project within medicine
Prediction and prevention of diseases, testing and treatment for inherited disorders, new medicines
