MISCONCEPTION CHAPTER HEREDITY AND VARIATION

3.1 CELL DIVISION

MISCONCEPTION SOURCES OF MISCONCEPTION

TRUE CONCEPT DESCRIPTION

Interphase is the resting phase of mitosis

- Interphase take along time to continue with others stage.

- The duration of time spent in interphase and in each stage of interphase is variable and depends on both the type of cell and the species of organism it belongs to. Most cells of adult mammals spend about 20 hours in interphase, this accounts for about 90% of the total time involved in cell division.

Interphase is the first stage in mitotic cell cycle

interphase is the phase in the cell cycle in which cell spends of its time to performs majority of its proposes including preparations for the cell division in which the cell grows and replicates its DNA.

3.2 Understanding the principles and mechanism of inheritance

Misconception Source of Misconception Correct Concept ExplanationDaughters inherit most of their characteristics from their mothers while boys inherit most of their characteristics from their fathers or females inherit most of their genes fromthe mothers, while boys inherit most of their genes from their fathers

Based on their experiences, they think thank they should inherited the characteristics from the person who have same gender with them.

No matter whichGender, mother and father will contribute 50% each from their gene to be inherited by their child.

Female sexual chromosomes are XX. While male sexual chromosome are XY. To determine their offspring sexual chromosome, Mendel cross can be applied. The law of Mendel should be followed: law of segregation and law of independent assortment of the gene from both parents. So, each parent (mother and father) will contribute 50% of their gene to be inherited by their child.

3.3 Understanding Sex determination and the occurrence of twins in human beings

MISCONCEPTION SOURCES OF MISCONCEPTION

TRUE CONCEPT DESCRIPTION

1) The size of X and Y chromosome are the same

2) Autosomes are paired somatic chromosomes that play part in the sex determination

3) Autosome are sex chromosome

students may assume that autosome will determine the sex of human because autosome has genes that carry the characteristic of a person. The second misconception occur because students are not been able to see the real chromosome. Schematic diagram usually show the same size for chromosome X and Y

1) The size of X chromosome is bigger than Y chromosome

2) Autosome are paired somatic chromosomes that play no part in the sex determination

3) Autosome are non sex chromosome

From the 23 pairs of chromosomes in a human somatic cell, 22 pairs of it are autosome while only one pair is sex chromosome. The sex chromosome will determine the sex of a person. Male sex chromosome are XY. So, male somatic cell contains 22 pairs of autosomes with one X chromosome and one Y chromosome, i.e. 44 + XY. Female sex chromosome is XX. So, female somatic cell contains 22 pairs of autosomes and two X chromosome, i.e. 44 + XX . The X chromosome is bigger than the Y chromosome and because females have two copies, one X chromosome is largely switched off or inactivated.

MISCONCEPTIONS SOURCES OF MISCONCEPTION

TRUE CONCEPT DESCRIPTION

Klinefelter’s syndrome is a male that have appearance like female

Small shoulder male and some with breast

This due to hereditary disease has 1 extra X choromosome.

1 extra chromosomes XXY Normally males suffer from this

hereditary disease. They fail to produce sperm, therefore they are infertile.

Have 47 chromosome. This occurrence happens because X

chromosome fail to separate during meiosis.

Turner Syndrome is a female that cannot give birth.

We would not be able to see person that suffer this heredity cannot give birth after married and not undergo menstrual cycle.

This is due to chromosomes mutation occurs in female. –monosomy X.

A person who suffers from this heredity disease lacks one X chromosome.

People with Turner syndrome have only 1 sex chromosomes which is XO.

Only females sufer from this hereditary disease.

They posess features like infertility, short stature, and do not experience menstrual cycle.

When provided with estrogen replace therapy, girls with Turner syndrome do develop secondary sex characteristics.

Most have normal intelligence.

3.4 Understanding Mutation

3.6 Variation

Misconception Source of Misconception True Concept Description

Continuous variation means something that change through your life.

The examples of continuous variation are skin colour, height, body weight and others.

For example:

Our body height and body weight are keep changing as we grow. From the baby stage to the adult stage.

Continuous variation means characteristic which do not show obvious variation in trait among individuals of same species.

Although this is true of the measurements students are likely to have made to illustrate this, it is not the correct meaning of the term. Actually, Continuous variation refers to characteristic which do not show obvious variation in a trait among individuals of the same species.

Intelligence is an example of discontinuous variation.

Our environment gives the effect to how we thinks and we always make a conclusion based on what we see, for example :

If the father and the mother are genius, absolutely their daughter or son is genius also.

Intelligence is an example of continuous variation.

Intelligence is not a discontinuous variation because intelligence is cause by the environment. For example, the food that we eat. There are no specific genes that carry intelligence trait.

Variation between species is a result of adaptation to

Based on our prior knowledge,

Body weight is caused by the food we eat.

Variation between species is a result of adaption to environment and genetic inheritance.

There are two factors that cause variation :

1. Genetic

This factor determines variation inherited from parents. Examples of variation caused by this factor are blood group

environment instead of inheritance. Body skin is caused by exposure to

the sunlight.

and eye colour.

2.Environment

This factor produces variation caused by food, exposure to sunlight, climates and weather such as body weight and height.

For example: Variation in individual’s weight are the result of food intake and genes.