Topic 3 - genetics

Question 1

What is meiosis?

Answer 1

• produce haploid gamete cells
• only have one copy of each chromosome.
• forms four non-identical cells from one cell.

Question 2

Describe meiosis

Answer 2

• diploid parent cell with 46 chromosomes
• Chromosomes make non- identical copies of themselves
• similar chromosomes pair up ( still non- identical)
• sections of DNA get swapped
• pair of chromosomes divide & become daughter cells
• chromosomes divide again into 4 haploid gamete non- identical cells ( males make sperm and women make egg)

Question 3

Differences between mitosis and meiosis

Answer 3

• meiosis produces 4 daughter cells & mitosis produces 2 daughter cells
• mitosis produces genetically identical cells, meiosis produces genetically different
• mitosis produces diploid cells and meiosis produce haploid cells

Question 4

Structure of DNA

Answer 4

• made up of nucleotides w/ one sugar and one phosphate molecule
• complimentary matching base pairs A,T & C,G
• double helix twist

Question 5

What is a gene?

Answer 5

• short section of DNA. Each gene codes for many amino acids, which are joined together to make a specific protein.
• There are 20 types of amino acid

Question 6

What is a genome?

Answer 6

• all the genetic information (DNA) of a single organism

Question 7

Describe How to extract DNA from a fruit

Answer 7

• mix cold water, half a teaspoon of salt and washing up
  liquid– heat mixture for 5-10 minutes.
• chop into small pieces & Pulverise fruit
• Add solution from Step 1 to fruit.
• Filter solution and pour filtrate into a test tube.
• Add pineapple juice to filtrate and allow to rest for a few minutes.
• Add cold ethanol to the solution and wait.
  – white precipitate should form from fruit– this is the DNA

Question 8

Why do we add (pineapple) juice and ethanol in the ‘how to extract DNA from fruit experiment.’

Answer 8

• juice
• contains an enzyme that breaks down proteins attached to DNA.
• helps us see DNA more clearly
• ethanol
  causes DNA to precipitate out of the solution - makes it visible

Question 9

What is the non coding part of DNA?

Answer 9

• doesn’t code for proteins– some responsible for determining if gene is used to form a protein or not

Question 10

What is a polypeptide ?

Answer 10

• amino acids linked by peptide binds

Question 11

Difference between phenotype & genotype ?

Answer 11

• genotype is the set of genes in our DNA which is responsible for a particular trait
• phenotype is the physical expression, or characteristics, of that trait (one you can see)

Question 12

How can Mutations change the sequences of bases in DNA?

Answer 12

• base is inserted into the code
• base is deleted from the code
• base is substituted

Question 13

How can Mutations change the sequences of bases in DNA?

Answer 13

• A base is inserted into the code
• A base is deleted from the code
• A base is substituted

Question 14

Mendel’s pea experiments

Answer 14

• got smooth peas, wrinkled peas, green peas & yellow peas and observed offspring to see which characteristics they’ d inherited
• Offspring have some characteristics that parents had because they
  inherit ‘​hereditary units​’ from each.
• unit received from each parent.
• can be dominant or recessive, cannot be mixed together.

Question 15

Different between dominant and recessive gene

Answer 15

• dominant
  Only one of two alleles needed for it to be expressed
• recessive
  Two copies needed for it to be expressed

Question 16

What is zygote?

Answer 16

• stage of development right after fertilisation from 2 gamete cells
• diploid cell

Question 17

What are alleles?

Answer 17

• different from of the same gene

- allele that codes for a damaged part of a protein can cause an illness

Question 18

​what is codominance ?

Answer 18

2 dominant alleles that can be expressed ​together ​in the same individual.

Question 19

What is genetic variation?

Answer 19

​different characteristics because of random mutation​ and ​sexual reproduction​.
- produces new phenotypic characteristics,

Question 20

What is environmental variation?

Answer 20

​- characteristics changed by organism’s environment, but changes are generally not ​heritable

Question 21

Benefits of human genome

Answer 21

• improved understanding ​genes linked to different types of disease
• helped in treatment of inherited disorders
• helped in ​tracing human migration patterns​ from the past.

Question 22

Effects of genetic mutation on phenotype

Answer 22

• some mutations, can rarely affect phenotype - some do though
• changing one base can change one amino acid in a protein. If an enzyme, can change shape of the active site​ — substrates can no longer fit

Question 23

Explain natural selection

Answer 23

• process whereby organisms better adapted to their environment tend to survive and produce more offspring
• • leads to evolution

Question 24

Family pedigree symbols

Answer 24

• square means man, coloured square means infected man, half coloured in means recessive, carries but doesn’t affect him – same w/ women but they are circles

Question 25

ABO Blood Group Inheritance

Answer 25

• A and B are co dominant and O is recessive

- O is universal donor

Question 26

Benefits of human genome project?

Answer 26

• understanding of genes linked to different types of disease
• help treatment of inherited disorders
• help in tracing human migration patterns from the past

Question 27

Describe protein synthesis

Answer 27

DNA contains the genetic code for making a protein, but cannot move out of the nucleus as it is too big.

• mRNA nucleotides are then joined together, creating a new strand called the mRNA strand. This is a ​template​ of the original DNA.
• enzyme called ​RNA polymerase​ binds to ​non-coding DNA​ located in front of a gene on the DNA strand.
• The two strands of DNA pull apart from each other, and ​mRNA nucleotides​ match to their complementary base on the strand. It becomes (A,U and C,G)
• mRNA then moves out of the nucleus to the cytoplasm and onto structures called ​ribosomes​.
• At the ribosomes, the bases on the mRNA are read in ​triplets​ to code for an amino acid (first three bases code for one amino acid etc).
• corresponding amino acids are brought to the ribosomes by ​tRNAs - transport RNAs
• . These amino acids connect together to form a polypeptide
• When chain is complete the protein forms a unique 3D structure, which is the ​final protein​.