Inheritance Genes And Cell Division

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Chromosomes, Genes & Proteins

Chromosomes are thread-like structures in the nucleus made of DNA.
A gene is a short length of DNA on a chromosome that codes for a specific protein (e.g., collagen, enzyme, hormone).
Alleles are alternative forms of a gene (e.g., blue, green, brown alleles for eye colour).
Genes determine characteristics by coding for proteins.

The Inheritance of Sex

Sex is determined by sex chromosomes: females are XX, males are XY.
Only males can pass on a Y chromosome, determining the child's sex.
Half of sperm carry X, half carry Y; if X fertilises egg (X), offspring is female (XX); if Y fertilises egg, offspring is male (XY).
Punnett square for sex inheritance shows 50% probability of each sex.

Control of Gene Expression (Extended)

Diploid cells have two sets of chromosomes (e.g., human body cells: 46 chromosomes).
Haploid cells have one set of chromosomes (e.g., human gametes: 23 chromosomes).
Gametes (sperm and egg) are haploid; fertilisation restores diploid number.

Mitosis (Extended)

Mitosis is nuclear division producing genetically identical diploid cells.
Chromosomes replicate before division, ensuring each daughter cell has the same number of chromosomes.
Mitosis is used for growth, repair of damaged tissues, replacement of cells, and asexual reproduction.

Meiosis (Extended)

Meiosis is a reduction division that halves chromosome number from diploid to haploid.
It produces four genetically different haploid cells (gametes).
Meiosis ensures genetic variation and maintains constant chromosome number after fertilisation.

Monohybrid Inheritance

Inheritance is the transmission of genetic information from parents to offspring.
Genotype is the combination of alleles; phenotype is the observable characteristic.
Dominant allele masks a recessive allele; recessive only shows when homozygous.
Homozygous = two identical alleles; heterozygous = two different alleles.
Monohybrid inheritance involves a single gene; Punnett squares predict offspring ratios.
Example: tall (T) dominant over short (t); cross TT × tt gives all Tt (tall); Tt × Tt gives 3:1 ratio tall:short.
Pedigree charts trace inheritance patterns through families, using squares (males) and circles (females).

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Practice questions

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1.Where are chromosomes located in a cell?
Easy
- AIn the cytoplasm
- BIn the nucleus
- COn the cell membrane
- DIn the mitochondria
2.What is a short length of DNA that codes for a specific protein called?
Easy
3.Biological females have the sex chromosomes XY.
Easy
True or false?
4.Complete the sentence about cell division.
Easy
Mitosis produces genetically ____ cells.
5.How many chromosomes are in a human diploid cell?
Easy
- A46
- B41
- C51
- D56
6.Match each cell division type to its description.
Medium
- Mitosis
- Meiosis
- Produces genetically identical cells
- Produces genetically different cells
- Reduces chromosome number by half
7.Arrange the following events in the correct order for meiosis:
Medium
- Chromosomes replicate
- Homologous chromosomes separate
- Cell divides twice
- Four haploid cells are formed
8.In a monohybrid cross between two heterozygous tall plants (Tt x Tt), what is the expected phenotypic ratio?
Medium
- A1:2:1
- B3:1
- C1:1
- D9:3:3:1

More questions

9.What term describes an individual having two different alleles of a gene?
Easy
10.A genetic cross is carried out between a homozygous recessive short plant and a heterozygous tall plant. What is the probability that an offspring will be short?
Medium
- A0%
- B25%
- C50%
- D100%
11.What term describes an alternative form of a gene?
Easy
12.In the Punnett square below, what is the genotype of the offspring in the top left square?
Medium
- ATT
- BTt
- CtT
- Dtt
13.A gene is a short length of DNA found on a chromosome that codes for a specific protein.
Easy
True or false?
14.Mitosis is used for growth, repair of damaged tissues, replacement of cells, and asexual reproduction.
Easy
True or false?
15.Meiosis results in two genetically identical cells.
Easy
True or false?
16.A dominant allele needs to be inherited from both parents in order for the characteristic to show up in the phenotype.
Medium
True or false?
17.Haploid nuclei contain two sets of chromosomes.
Easy
True or false?
18.The observable characteristics of an organism are called the genotype.
Easy
True or false?
19.In a Punnett square, the dominant allele is shown using a capital letter and the recessive allele is shown using the same letter but lowercase.
Easy
True or false?
20.Alleles are variations of the same gene.
Easy
True or false?
21.In a family pedigree diagram, males are indicated by circles and females by squares.
Easy
True or false?
22.Meiosis is a reduction division that halves the chromosome number from diploid to haploid.
Easy
True or false?
23.If the two alleles of a gene are different, the individual is described as homozygous.
Easy
True or false?
24.Match each term with its correct description.
Medium
- Gene
- Allele
- Chromosome
- Thread-like structure made of DNA carrying genetic information
- Short length of DNA that codes for a specific protein
- Alternative form of a gene
25.Arrange the following events in the correct order for a monohybrid cross between two heterozygous parents (Tt x Tt).
Medium
- Determine parental genotypes
- Split alleles for each parent and add to Punnett square
- Fill in the Punnett square to find offspring genotypes
- Determine the phenotypic ratio from the offspring genotypes
26.Which of the following are true about meiosis? (Select all that apply)
Medium
- AIt produces genetically identical cells
- BIt is a reduction division
- CIt produces gametes
- DIt results in four cells
- EIt is used for growth and repair
27.In humans, the sex chromosomes of a biological female are XY.
Easy
True or false?
28.In a family pedigree chart, which shape is used to represent a female?
Easy
- ASquare
- BCircle
- CTriangle
- DDiamond
29.A cell has 12 chromosomes. After mitosis, each daughter cell has how many chromosomes?
Easy
- A6
- B12
- C24
- D3
30.What is the probability that a child will be male?
Easy
- A25%
- B50%
- C75%
- D100%
31.Which of the following are functions of mitosis? (Select all that apply)
Medium
- AGrowth
- BProduction of gametes
- CRepair of damaged tissues
- DAsexual reproduction
- EReduction of chromosome number
32.A gene codes for a specific protein. Which of these is an example of a protein a gene might code for?
Easy
- ACollagen
- BGlucose
- CCellulose
- DStarch
33.In the Punnett square below, what is the genotypic ratio of the offspring?
Medium
- A1:2:1
- B3:1
- C1:1
- D9:3:3:1
34.In a species of plant, the diploid chromosome number is 14. How many chromosomes would be present in a haploid gamete?
Easy
- A7
- B14
- C28
- D21
35.The diagram shows part of a family pedigree for a recessive genetic disorder (affected individuals have an orange/red outline). In the family on the left, an affected father and an unaffected mother have an affected daughter and an unaffected son. What must the unaffected mother's genotype be for the disorder allele?
Hard
- AHeterozygous (carrier)
- BHomozygous dominant
- CHomozygous recessive
- DCannot be determined from the pedigree
36.Meiosis results in the production of four genetically identical daughter cells.
Easy
True or false?
37.Match each cell division type to its correct description.
Medium
- Mitosis
- Meiosis
- Produces genetically identical cells
- Reduces chromosome number from diploid to haploid
- Produces four genetically different cells
38.Arrange the following events in the correct order for a monohybrid cross between two heterozygous parents (Tt × Tt) to determine the probability of offspring genotypes.
Medium
- Determine parental genotypes
- Fill in the Punnett square
- Split alleles for each parent
- Calculate the ratio of offspring genotypes
39.Which of the following statements about alleles are correct? (Select all that apply)
Medium
- AAlleles are different forms of the same gene
- BAn individual can have up to four alleles for a single gene
- CA dominant allele is expressed even if only one copy is present
- DA recessive allele is only expressed if two copies are present
40.In a species of bird, the diploid chromosome number is 80. How many chromosomes would be present in a cell after meiosis I?
Medium
- A40
- B80
- C20
- D160
41.In an investigation, a student placed a piece of onion root tip in a stain that makes chromosomes visible. Which region of the root tip should the student examine to find cells undergoing mitosis?
Easy
- ARoot cap
- BRegion of elongation
- CRegion of cell division (meristem)
- DRegion of maturation
42.A student investigates the effect of temperature on the rate of mitosis in onion root tips. They count the number of cells in mitosis per 100 cells at different temperatures. Which of the following are essential controls in this experiment? (Select all that apply)
Hard
- AUsing the same type of onion
- BCounting cells from the same region of the root tip
- CKeeping the roots in the dark
- DUsing the same stain for all samples
- EMeasuring the temperature with a thermometer
43.In a monohybrid cross between two heterozygous parents (Tt × Tt), the expected phenotypic ratio of offspring is 1:2:1.
Medium
True or false?
44.Match each term on the left with its correct description on the right.
Easy
- Haploid
- Diploid
- Allele
- Has two sets of chromosomes
- A variant of a gene
- Has one set of chromosomes
45.A pure breeding tall pea plant (TT) is crossed with a pure breeding short pea plant (tt). What percentage of the offspring will be tall?
Easy
46.Complete the sentences about chromosomes.
Medium
In a human body cell, there are ____ chromosomes. In a human gamete, there are ____ chromosomes.
47.What is the term for an individual having two different alleles of a gene?
Easy
48.Complete the sentence.
Easy
The sex chromosomes of a biological male are ____.
49.In a monohybrid cross between two heterozygous tall plants (Tt × Tt), what is the probability (as a percentage) that an offspring will be short?
Medium
50.What is the name of the structure that carries genetic information and is found in the nucleus of cells?
Easy
51.A cell has 8 chromosomes. After mitosis, each daughter cell has how many chromosomes?
Easy
52.How many chromosomes are in a human haploid gamete?
Easy
53.State two differences between mitosis and meiosis.
Medium
54.Describe two differences between mitosis and meiosis.
Medium
55.Describe how a Punnett square can be used to predict the probability of offspring inheriting a recessive condition from two heterozygous parents.
Hard
56.A pure breeding tall pea plant (TT) is crossed with a pure breeding short pea plant (tt). What percentage of the offspring will be tall?
Easy
- A100 %
- B90 %
- C120 %
- D110 %
57.In a monohybrid cross between two heterozygous tall plants (Tt × Tt), what is the probability (as a percentage) that an offspring will be short?
Medium
- A22 %
- B31 %
- C28 %
- D25 %
58.A cell has 8 chromosomes. After mitosis, each daughter cell has how many chromosomes?
Easy
- A9
- B7
- C8
- D10
59.How many chromosomes are in a human haploid gamete?
Easy
- A23
- B27
- C25
- D21

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