Unit 4 : Genetics

The largest organelle in a cell is the ____ .

The first thing to divide during cell division is the ____ which controls and directs the activities of the cell throughout life; it contains the ____ which is passed from generation to generation during reproduction.

Each ____ consists of ____, a huge molecule consisting of 2 ____ strands in the form of a double helix which runs ____ of the chromosome and is supported by ____ .

A pair of genes with the same alleles are called ____ .

When the ____ chromosomes have paired up closely, each pair is called a ____.

Crossing over occurs in ____ .

The four ____ cells produced in meiosis differ genetically from each other because of ____ & ____ .

Mutations occurring in the body cells of multicellular organisms are called ____ mutations.

A mutation is a change in the ____ or ____ of ____ which may result in a ____ of an organism.

Non - disjunction is the term given to the ____ and go to opposite poles during the nuclear division of the nucleus.

People with down syndrome have an extra chromosome __ , giving them a total of 47 chromosomes.

In chromosome mutations there is a change in the ____ or ____ of ____ . Gene mutations are changes in the ____ of ____ in the ____ of a gene.

Sickle cell anaemia is brought about by base substitution which is an example of a gene mutation. Here ____ is substituted with ____ which causes the mutation.

Haemoglobin, the ____ - transporting pigment of red cells, is made of 4 ____ molecules that interlock and form a compact molecule -two of the haemoglobin molecules are known as ____ and the other two as ____ .

The gene that codes for the amino acid sequence of beta haemoglobin occurs on chromosome ____ .

The gene that codes for beta haemoglobin is prone to a substitution of the base ____ to ____ in a codon for the amino acid glutamic acid.

Haemophilia is a ____ condition because the genes controlling the production of the blood proteins concerned are located on the ____ chromosome .

As in mitosis, chromosomes replicate to form chromatids during interphase, however, in meiosis __ ___ chromosomes ___ and by the end of meiosis ___ they have ___ but the chromatids they consist of do not separate until meiosis __.

Ways of checking for sickle cell anaemia in embryos are:

The effects on the properties of the haemoglobin molecule if this base substitution occurs are:

The inheritance of a single characteristic is known as a monohybrid cross.

If alleles for a gene are different, they are said to be ___.

The ___ is the way in which the ___ of an organism is expressed- including the ___ of the organism.

when both alleles are expressed they are known as ___.

A gene is a pair of alleles that both affect the phenotype of an organism when present in a heterozygote.

A gene is the basic unit of inheritance by which inherited characteristics are transferred from parent to offspring, consisting of a length of DNA on a chromosome.

Examples of recessive conditions controlled by genes on the X chromosome are :