Part D Mock Test — Heredity and Variation

Explanation

The graph shows a bell-shaped (normal) distribution of cassava plant heights.

The highest point (apex) of the graph represents the height with the greatest frequency.

The peak occurs at approximately 1.6 metres, meaning most of the cassava plants have this height.

Explanation

Continuous variations are variations within a population in which phenotypes may have any value between the extremes. Traits in the population tend to be quantitative. It is usually controlled by a lot of genes and strongly influenced by the environment. Examples of such phenotypic traits are height, weight, intelligence.

Explanation:

DNA profiling compares genetic material from the scene with that of a suspect to determine a match.

Explanation: Each type of a gene for a character is inherited from the mother and from the father and are on the same locus of the homologous chromosomes bearing them. The gene that expresses the character in the presence of the other is the dominant gene while the gene that is not expressed is the recessive gene.

Explanation:

A codon is a sequence of three DNA or RNA nucleotides that corresponds with a specific amino acid or stop signal during protein synthesis

Explanation: Poliomyelitis is caused by a pathogen (virus) and is transmitted by drinking or eating infected food.

Explanation: A DNA sequence is the precise order of nucleotides within a DNA molecule. DNA (Deoxyribonucleic acid) carries the genetic instructions for growth and development. DNA is composed of four nucleotide bases: Adenine, Thymine, Cytosine, and Guanine. These bases pair in a complementary fashion: Adenine pairs with Thymine, while Guanine pairs with Cytosine.

In DNA, base pairing follows Chargaff’s rules:

• Adenine (A) always pairs with Thymine (T) via two hydrogen bonds
• Guanine (G) always pairs with Cytosine (C) via three hydrogen bonds

Other combinations do not occur in standard DNA.

Explanation

Sex-linked genes are located on the X chromosome and result in X-linkage. Similarly, Y-linkage refers to the gene which is present on the Y chromosome. Since females are homogametic with XX chromosome and males have XY chromosome, the Y-linked traits are transmitted via males only.

Explanation: Diploid cells are those that contain a complete set or (2n number) of chromosomes, whereas haploid cells are those that contain half the number or (n-number) of chromosomes. The gametes have a haploid number of chromosomes; therefore, if the diploid number of chromosomes of an organism is 16, each gamete would be 8.

Explanation: Hemophilia is a bleeding disorder that slows the blood clotting process. People with this disorder experience prolonged bleeding or oozing following injury, surgery, etc. It's an inherited condition that affects the body's ability to produce clotting factors.

Explanation: A continuous variation is a characteristic of any species that shows changes gradually over a range of values. Size, weight, height and colour are characteristics that change gradually over a range of values and thus have numerous possible values within a range.

Explanation

Since they are of the same specie it is 'inbreeding'. Crossbreeding involves diverse species.

Explanation

According to the principles of Mendel, this is the ability of two contrasting alleles to interact and produce a heterozygous phenotype that is different from the two homozygous phenotypes

Explanation: The ability to roll the tongue is a physiological variation in which there are two extreme values for which the individual can fall into either a tongue roller or not. It is therefore a discontinuous variation.

Explanation: The types of variations found in fingerprints are arches, (which occur in about 5% of the encountered fingerprints), Loops, Whorls, Plain arch, Tented arch, Radial loops, Ulnar loops, Double loop and Compounds.

Explanation: The DNA is the fastest and most accurate method for determining paternity. Through replicating the DNA or sequencing (PCR), the closeness between two individuals can be determined by looking at the genetic matches (similar banding patterns on the DNA) between the potential father and child.

Explanation

Phenotype is the sum total of all observable features of an organism i.e. the physical, physiological and behavioural traits e.g. height, weight, skin colour.

Genotype: This term is used to describe those traits or sum total of genes inherited from both parents.

Your answer is correct.

Explanation:

Haemophilia is an X-linked recessive disorder.

• The man is affected: XʰY
• The woman is affected (double recessive): XʰXʰ

Punnett cross:

All daughters (XʰXʰ) are affected, and all sons (XʰY) are affected.
Therefore, 100% of the offspring would have haemophilia.

Explanation

ABO blood groups in humans are controlled by the gene l. It has three alleles, IA, IB and I

Explanation: This is because cross-fertilization in sexual reproduction leads to a new combination of genes from the male and female gametes. More so the male and female gametes were products of crossing over or exchange of genes at the chiasmata during their formation.

Explanation:

Dog II acquired the short tail trait by accident and therefore will not be inherited because the phenotype is caused by environmental factors, not genetic factors.

Explanation:

The result of the cross can best be illustrated using genetic diagrams.

• Normal Winged – NN
• Short winged – nn

Phenotype:

• All the flies are normal-winged (i.e. 4 normal winged)

Phenotype:

• 3 normal winged
• 1 short winged

⇒ \(\Large \frac{3}{4} \normalsize \: are\: normal \: winged\)

Explanation: Weight, fingerprint and body shape have wide ranges in which an individual can fit into and are morphological or continuous variations.

Morphological variations in humans encompass a wide range of physical traits, including height, weight, eye and hair color, facial features, fingerprints, and even subtle variations in bone shapes and internal structures

Explanation

To properly identify the genes, we need to understand that G stands for the dominant trait for greyness, and g - the recessive trait for greyness. Hence:

I = GG

II = Gg

III = Gg

IV = gg

Explanation:

The genotype is the part of the genetic makeup of a cell, and therefore of any individual, which determines one of its characteristics.

An allele is a variant form of a given gene. It is one of two or more versions of a known mutation at the same place on a chromosome.

A chromosome is a threadlike structure of nucleic acids and proteins found in the nucleus of most living cells, carrying genetic information in the form of genes.

The term phenotype refers to the observable physical properties of an organism; these include the organism's appearance, development, and behaviour.

Explanation

Acquired characteristics (or characters) are those changes in the structure or function of an organism that are the result of use, disuse, environmental influences, disease, mutilation, and so forth, such as a muscle that is enlarged through use or mice that have their tails cut off.

Explanation: 

The “possession of facial hair in adult humans” is best described as a sex-influenced (sex-limited in expression) trait. The genes influencing facial hair may be present in both sexes, but the trait is expressed mainly in males because testosterone stimulates the development of facial hair after puberty. Therefore, the trait is closely associated with sex, even though it is not a standard X-linked example like colour blindness.

Explanation: Using a Punnett square

Your answer is correct.

Explanation: Inbreeding is the crossing of closely related individuals e.g. father × daughter, son × mother, brother × sister. It helps to maintain desirable traits. Outbreeding is the crossing of two completely unrelated individuals for the combination of desirable traits in one individual.

Your answer is correct.