inheritance

Question 1

what is inheritance

Answer 1

The transmission of genetic information from generation to generation

Question 2

what is a chromosome

Answer 2

a thread of DNA, made up of a string of genes

Question 3

what is a gene

Answer 3

a length of DNA that is the unit of heredity and codes for a specific protein. A gene may be copied and passed on to the next generation

Question 4

what is an allele

Answer 4

any of two or more alternative forms of a gene

Question 5

what is a haploid nucleus

Answer 5

a nucleus containing a single set of unpaired chromosomes (e.g. sperm and egg)

Question 6

what is a diploid nucleus

Answer 6

a nucleus containing two sets of chromosomes (e.g. in body cells)

Question 7

inheritance of gender in humans

Answer 7

woman’s gamete can only carry an “X” chromosome, and a male gamete can carry either an “X” or “Y” chromosome; females are “XX” while males are “XY”. There is always a 50% chance of getting a boy and vice versa.

Question 8

function of DNA

Answer 8

control cell functions by controlling production of proteins, antibodies and receptors for neurotransmitters

Question 9

makeup of DNA

Answer 9

DNA has 2 long strands and 4 nucleotides, AT and CG

Question 10

process of protein synthesis

Answer 10

Made from long chains of amino acids (20)

DNA bases are read as triplets

DNA is found in the nucleus

Protein synthesis happens on ribosome in cytoplasm

mRNA carries information from DNA to ribosome

When a protein is made, mRNA is made in the nucleus, copying the base sequence

mRNA moves out of the nucleus into the cytoplasm and attaches to the ribosome

ribosome assembles amino acids into protein molecules

the specific order of amino acids is determined by the sequence of bases in the mRNA

Question 11

why are some genes in particular cells not present

Answer 11

All body cells in an organism contain the same genes, but many genes in a particular cell are not expressed because the cell only makes the specific proteins it needs

Question 12

what is mitosis

Answer 12

The nuclear division giving rise to genetically identical cells in which the chromosome number is maintained by the exact duplication of chromosomes.

Question 13

what is mitosis needed for

Answer 13

Growth: in animals each tissue provides its own new cells when they are needed.

Repair of damaged tissues: for example, when you cut your skin, mitosis provides new cells to cover up cut.

Replacement of worn out cells

Asexual reproduction: in plants

Question 14

what are stem cells

Answer 14

unspecialized cells that divide by mitosis to produce daughter cells that can become specialized for specific functions

Question 15

what is meiosis

Answer 15

Reduction division in which the chromosome number is halved from diploid to haploid

Gametes are the result of meiosis

Meiosis results in genetic variation so the cells produced are not all genetically identical.

Question 16

what is a genotype

Answer 16

genetic makeup of an organism in terms of the alleles present (e.g. Tt or GG)

Question 17

what is a phenotype

Answer 17

physical or other features of an organism due to both its genotype and its environment (e.g. tall plant or green seed)

Question 18

relation between genotypes and phenotypes

Answer 18

genotype + environment + random variation → phenotype

Question 19

what is homozygous

Answer 19

having two identical alleles of a particular gene (e.g. TT or gg). Two identical homozygous individuals that breed together will be pure-breeding

Question 20

what is heterozygous

Answer 20

having two different alleles of a particular gene (e.g. Tt or Gg), not pure-breeding

Question 21

what is dominant

Answer 21

an allele that is expressed if it is present (e.g. T or G)

Question 22

what is recessive

Answer 22

an allele that is only expressed when there is no dominant allele of the gene present (e.g. t or g)

Question 23

what is codominance

Answer 23

when neither of two alleles is dominant to each other.

Question 24

what are the blood group alleles

Answer 24

There are three alleles for blood group given by the symbols I^a, I^b and I^o.

I^a and I^b are co-dominant giving blood group AB or I^aI^b, and both dominant to I^o.

Question 25

what is a sex-inked characteristic

Answer 25

a characteristic in which the gene responsible is located on a sex chromosome and that this makes it more common in one sex than in the other

Colour blindness as an example of sex linkage