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.
Nucleus | hereditary material
Nucleus | gene
Cytoplasm | chromosome
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 ____ .
Chromosome | DNA | paired | the full length | protein
Chromosome | DNA | separate | for half | histones
Chromatid | DNA | linked | the full length | protein
A pair of genes with the same alleles are called ____ .
When the ____ chromosomes have paired up closely, each pair is called a ____.
Homologous | bivalent
Homozygous | Bivalent
Crossing over occurs in ____ .
The four ____ cells produced in meiosis differ genetically from each other because of ____ & ____ .
Haploid | Independent assortment | Crossing over
Diplod | Independent assortment | Crossing over
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.
Type | genetic structure | the cell | change in the characteristics
Amount | chemical structure | DNA | change in the characteristics
Amount | base structure | DNA | change in the functions
Non - disjunction is the term given to the ____ and go to opposite poles during the nuclear division of the nucleus.
Failure of a pair chromatids to separate
Success of a pair of chromatids separating
Failure of a pair of chromosomes to separate
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.
Number | sequence | bases | sequence | genes | DNA
Number | sequence | genes | sequence | bases | DNA
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.
Glu | Pro
Glu | His
Va | Glu
Leu | Val
Thr | Pro
Glu | Val
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 ____ .
Oxygen | protein | alpha | beta
Carbon dioxide | hydrogen | alpha | beta
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.
A | T
T | A
C | A
A | C
G | C
C | G
C | T
Haemophilia is a ____ condition because the genes controlling the production of the blood proteins concerned are located on the ____ chromosome .
Sex - linked | X
Sex - linked | Y
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 __.
II | homologous | pair up | I | cross over | II
I | homologous | separate | I | separated | I
I | homologous | pair up | I | separated | II
I | homozygous | separate | II | separated | I
Ways of checking for sickle cell anaemia in embryos are:
blood test on the mother
chorionic villus sampling
blood test on the father
X ray of the embryo
The effects on the properties of the haemoglobin molecule if this base substitution occurs are:
they tend to clump together
they form short fibres that distort the red cells into plump disk shapes.
they become low in viscosity
they form unusually long fibres that distort the red cells into sickle shapes.
they become too large for the blood vessels.
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.
genotype | phenotype
phenotype | genotype
when both alleles are expressed they are known as ___.
this can never happen.
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 :