Name: …………………………………………………… Class: ……. Chapter 3 Exercise 1 Learning Area: Heredity and Variation Learning Objective: Understanding cell division 1. The diagram below shows the process of mitosis. Fill in the blanks with the words given. Replication align nucleus membrane divide two shorten thicken Chromatid same separate move Stages of mitosis Simple explanation ∙ Chromosomes in the nucleus ………………. , …………… and are more visible. ∙ ……………………of chromosomes occur. ∙ Each strand of chromosome is called a ……………………. ∙ Chromosomes ......................... themselves in the centre of the cell. ∙ The ……………………………………….. disappears. ∙ Chromatids …………………… and ……………………… to the opposite ends of the cell. ∙ At the same time, the cell starts to ………………………….. 3-1 Score: .…/12 x 100 = ……….. %
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1. The diagram below shows the process of mitosis. Fill in the blanks with the words given.
Replication align nucleus membrane divide two shorten thicken Chromatid same separate move
Stages of mitosis Simple explanation
∙ Chromosomes in the nucleus ………………. , ……………
and are more visible.
∙ ……………………of chromosomes occur.
∙ Each strand of chromosome is called a …………………….
∙ Chromosomes ......................... themselves in the centre of the cell.
∙ The ……………………………………….. disappears.
∙ Chromatids …………………… and ……………………… to the opposite ends of the cell.∙ At the same time, the cell starts to …………………………..
∙ The nucleus membrane forms again.∙ ………………………… daughter cells are formed.∙ Each progeny cell has the ………………………. number of chromosomes as the parent cell.
Name: ……………………………………………………… Class: …..Chapter 3Exercise 3Learning Area: Heredity and VariationLearning Objective: Understanding the principles and mechanism of inheritance.
1. Complete the table with the correct definition.
TERMS DEFINITIONS
……………………Describes the characteristics traits of an organism, including the physical and the physiological
…………………… Organism which has two identical genes. Example: TT or tt.
…………………… Composition of gene in an organism
……………………. Thread-like structure present in the nucleus of a cell
……………………..A gene which is weak and its effect can be masked by a dominant gene
…………………….An organism which has one dominant gene and one recessive gene for a certain characteristic. Example: Bb ( B = dominant gene for black fur , b = recessive gene for white fur )
……………………Unit carrying a characteristic trait which exists in pairs in a chromosome.
…………………….Organism which has two different members of the same gene. Example: Tt.
…………………….Exchange of genes when two chromatids cross giving rise to genetic variation.
…………………….. A gene which masks the effect of a weaker gene
2. A man with black hair (Bb) marries a woman with blonde hair (bb). Complete a schematic diagram to show the cross between a men who is heterozygous for black hair (Bb) and a woman with blonde hair (bb)
B : Gene carrying black hair trait (dominant) b : Gene carrying blonde hair trait (recessive)
Father Mother Parent
Meiosis
Gamete
Fertilisation
Offspring genotype
Offspring phenotype
Based on the schematic diagram, determine the phenotype ratio of their offspring
……………………………….
3-6
Bb bb
Name: …………………………………………………. Class: ……Chapter 3Exercise 4Learning Area: Heredity and VariationLearning Objective: Understanding sex determination and the occurrence of twins in human being.1. Complete the following table.
WOMAN MANSomatic cell Ovum Somatic cell Sperm
Autosomes(non-sex
chromosomes)……………….. 22 44 ……………………
Sex chromosomes
XX ………………. ……………….. X or Y
Total 44 + XX(46 chromosomes)
…………………(23 chromosomes)
………………….(46 chromosomes)
22 + X or22 + Y
(23 chromosomes)
2. The schematic diagram below shows sex determination of an offspring. (a) Complete the schematic diagram.
Father Mother
Parents :
Meiosis
Gamete :
Fertilisation
Offspring :
Sex: …………….. ……………. …………… ……………
(b) Based on the schematic diagram above, fill in the blanks with suitable answer.
(i) The probability ( in percentage ) of a son or a daughter being born at each birth is ……………………
(ii) The sex of a zygote depends on whether the ovum is fertilized by a sperm carrying an X-chromosome or a sperm carrying a Y-chromosome. If the ovum is fertilized by a sperm carrying a Y-chromosome, a …………….. zygote will be produced.
3-7
Score: .…/33 x 100 = …… %
44 + XY 44 + XX
……… …….. ………. ……….
………... ………. ………. ………..
3. The comparison between identical twins with non-identical twins:
[A] Lack of a protein in the blood that is necessary for blood-clotting
Down’sSyndrome
……...
[B] The mutant genes cause the red blood cells to be sickle shaped. The patient is pale because the red blood cells carry little oxygen due to lack of haemoglobin and are easily broken.
Colour-blindness ………
[C] A female who has only one X chromosome. The female has no ovaries and menstrual cycle.
Turner’sSyndrome
………
[D] Hereditary lack of pigmentation in an organism. The animals or human beings have no colour in their skin, hair or eyes.
Sickle-cellanaemia
……..
[E] Possession of an extra chromosome 21. The child has short neck, short nose, downward-sloping eyes and protruding tongue.
Klinefelter’sSyndrome
……..
[F] The existence of a recessive gene that is defective and causes an inability to see and differentiate between red and green colour
Haemophilia………
[G] Presence of three sex chromosomes (XXY) instead of the usual two. Males are sterile and have small testes
3-9
Score: .…/7 x 100 = …… %
Name: ………………………………………………… Class: ……Chapter 3Exercise 6Learning Area: Heredity and VariationLearning Objective: Evaluating the effects of genetic research on human life.
1. Complete the table with the correct answer.
Technique Explanation
………………
The techniques involved in altering the characteristics of an organism by inserting genes from another organism into its DNA.
………………The crossing of two parents, each with some good traits, to produce offspring with the good traits of both parents.
……………….A coordinated international project, begun in 1988 to map the entire human genome so that the genes could be isolated and sequenced. It involved the production of a DNA library.
………………..The application of genetic engineering techniques to alter or replace defective genes.
…………………The process of producing offspring asexually from a single parent.
…………………The growth of the tissues of living organisms outside the body in a suitable culture medium.