Genetics

Question 1

What produces gametes?

Answer 1

Meiosis

Question 2

Where does meiosis happens?

Answer 2

In the reproductive organs; Ovaries and testes.

Question 3

Explain the first division in meiosis

Answer 3

• The cell duplicates its DNA
• The cell divides into two
• The chromosomes line up in pair at the centre of the cell
• One chromosome in a pair comes from each parent
• The pairs are then pulled apart so each new cell has one copy of each chromosome
• Each new cell now has a mixture of the mother’s and father’s chromosomes
• This creates genetic variation

Question 4

Explain the second division in meiosis

Answer 4

• The chromosomes line up in the centre of the cell
• The chromatids are pulled apart
• You get four haploid daughter cells
• The gametes are genetically different

Question 5

What are the advantages of asexual reproduction?

Answer 5

• It is faster
• Only one parent is needed
• Make use of resources

Question 6

What are the advantages of sexual reproduction?

Answer 6

• Genetic variation so easier to adapt to the environment

- not genetically identical

Question 7

What are the disadvantages of asexual reproduction?

Answer 7

• Genetically identical so there is no genetic variation

Question 8

What are the disadvantages of sexual reproduction?

Answer 8

• A mate is needed so it takes longer
• More time and energy
• Slower growth

Question 9

What are DNA made up of?

Answer 9

They are polymers made up of lots of repeating units of nucleotides.

Question 10

Explain the structure of DNA

Answer 10

• It has a double helix shape
• Has sugar-phosphate backbone
• There are four bases - adenine, thymine, cytosine and guanine
• The bases have complementary base pairing
• Adenine is complementary to Thymine
• Cytosine is complementary to Guanine
• The complementary bases are held together by weak hydrogen bonds

Question 11

Where is DNA stored?

Answer 11

In the chromosome

Question 12

Explain the structure of the chromosomes

Answer 12

• Long coiled up molecules of DNA

- Found in the nucleus of eukaryotic cells

Question 13

Describe the practical of extracting DNA from fruit cells

Answer 13

• Mash strawberries an put in beaker containing detergent and salt and mix well
• Filter the mixture to get the big insoluble bits out of the cell out
• Add ice-cold alcohol to mixture
• The DNA will come out the solution as it is not soluble in cold alcohol.
• It will appear as a stringy white precipitate

Question 14

How are proteins made?

Answer 14

By reading the code in DNA

Question 15

What are proteins made of?

Answer 15

Amino acids

Question 16

Homozygous meaning

Answer 16

The alleles are the same

Question 17

Heterozygous meaning

Answer 17

The alleles are different

Question 18

How are proteins made?

Answer 18

Made by reading the code in DNA

Question 19

What are genes?

Answer 19

Sections in DNA that code for a certain protein.

Question 20

What decides the order of the amino acids in a protein?

Answer 20

The order of bases in a gene.

Question 21

How are amino acids coded for?

Answer 21

By a sequence of three bases called a base triplet. The amino acids join together to make protein following the order of the bases.

Question 22

What is a mutation?

Answer 22

A random change in an organism’s DNA base sequence.

Question 23

What are the bases used in protein synthesis?

Answer 23

Guanine and Cytosine pair up

Uracil and Adenine pair up

Question 24

What is mRNA?

Answer 24

Is a polymer of nucleotide, but is shorter and single stranded

Question 25

What is RNA polymerase?

Answer 25

Is the enzyme involved in joining RNA nucleotides to make mRNA.

Question 26

Explain the stage of transcription in protein synthesis

Answer 26

- RNA polymerase binds to a region of non-coding DNA - The DNA is unzipped by the enzyme helicase - The RNA polymerase moves along one strand of the DNA - The coding DNA in the gene is used as a template for the mRNA making. - Base pairing is ensured between the DNA and RNA ensures that mRNA is complementary to the gene - When done the mRNA molecules move out the nucleus pores and joins with the ribosome

Question 27

Explain the stage of translation in protein synthesis

Answer 27

- Amino acids are brought to the ribosomes by tRNA - The order of the base triplets matches the order of amino acids brought to the membrane - Part of the tRNA (anticodons) is complementary to the codon for amino acids - The amino acids are joined together by the ribosomes and this makes a polypeptide (protein)

Question 28

What did Mendel do with the pea plants?

Answer 28

He crossed a dwarf pea plant and a tall pea plant but all their offspring's were tall pea plants. He then bred two of these tall pea plant but two of their offspring's were tall and one was a dwarf pea plant. This showed that the height characteristics in pea plants were determined by separately inherited passed on from each parent.

Question 29

What did Mendel's pea plant experiment show?

Answer 29

- Characteristics in plants are determined by hereditary units - These units are passed on to offspring's from both parent - These units can be dominant or recessive

Question 30

What is an allele?

Answer 30

2 versions of each gene present in the pair of chromosomes.

Question 31

How many chromosome are in the body?

Answer 31

46 chromosomes which make 23 pairs