17 - Inheritance

Question 1

Define gene and allele

Answer 1

A length of DNA that codes for a protein (3)
An alternative form of a gene (2)

Question 2

Explain what chromosomes are made of

Answer 2

Chromosomes are made of DNA (2)
which contains genetic information in the form
of genes (3)

Question 3

Describe the inheritance of sex in humans with reference to X and Y chromosomes

Answer 3

Sex is determined by a sex chromosome pair (2)
Females have a pair of XX sex chromosomes, while males have a pair of XY sex chromosomes (3)

Question 4

Explain what the sequences of bases in a gene determine, and how different sequences of amino acids differ

Answer 4

The sequence of amino acids used to make a specific protein (2)
Different sequence of amino acids, different shape of resulting protein (2)
specific protein (1)

Question 5

Explain how DNA controls cell function

Answer 5

By controlling the production of proteins (4)
incl. enzymes, membrane carriers, receptors for neurotransmitters, AVP (name 2) (1)

Question 6

Explain how a protein is made

Answer 6

The gene that codes a particular protein has its genetic code transcribed onto an mRNA molecule (2)
mRNA molecules are made in the nucleus and move to the cytoplasm (1)
The mRNA passes through ribosomes which assemble amino acids into protein molecules (1)
The specific sequence of amino acids is determined by the sequence of bases in the mRNA (1)

Question 7

Explain why different body cells in an organism produce different proteins, even though most of them contain the same genes

Answer 7

Many genes in a particular body cell are not expressed (2)
because the cell only makes the specific proteins it needs (3)

Question 8

State the differences between a haploid and diploid nucleus

Answer 8

Haploid nuclei contain a single set of chromosomes (2)
Diploid nuclei contain two sets of chromosomes (2)
with a pair of each type of chromosome (1)
(excl. 23/46 chromosomes, not human-specific)

Question 9

Define mitosis

Answer 9

Nuclear division/division of nuclei of cells (3)
producing genetically identical cells (2)

Question 10

State uses of mitosis

Answer 10

Mitosis is used in growth, repair of damaged tissues, replacement of cells, asexual reproduction (2, 4, 5 for 1, 2, 3 points made)

Question 11

Describe mitosis in stem cells

Answer 11

Stem cells are unspecialized cells that divide by mitosis (2)
to produce daughter cells (1)
that can become specialized for specific functions (2)

Question 12

Define meiosis

Answer 12

Nuclear division in which the chromosome number (from parent cell to daughter cell) is halved (from diploid to haploid) (3)
producing genetically different cells (2)

Question 13

Define inheritance

Answer 13

The transmission of genetic information (3)
from generation to generation (2)

Question 14

Define genotype and phenotype

Answer 14

The genetic makeup of an organism in terms of the alleles present (3)
The observable features of an organism (2)

Question 15

Define homozygous and heterozygous and state the differences between them

Answer 15

having two identical alleles of a particular gene (2)
having two different alleles of a particular gene (2)
two identical homozygous individuals are pure-breeding (whereas heterozygous individuals are never pure-breeding) (1)

Question 16

Define codominance

Answer 16

A situation in which both alleles in heterozygous organisms contribute to the phenotype (3)
Multiple alleles contribute to one trait (2)

Question 17

Explain the inheritance of ABO blood groups

Answer 17

Phenotypes are A, B, AB, and O blood groups (2)
Alleles are I/A, I/B, and I/O (1)
I/A and I/B are codominant, whereas I/O is recessive (additionally be able to use Punnett squares to predict phenotypes) (2)

Question 18

Define a sex-linked characteristic

Answer 18

A characteristic in which the gene responsible is located on a sex chromosome (2)
which makes the characteristic more common in one sex than another (3)