1

Summary

Biology Class 06

## ANALYSIS OF PREVIOUS YEAR QUESTION(5:05 PM):

|  |
| --- |
| Consider the following statements(Prelims 2021):   - (1) Adenoviruses have single-stranded DNA genomes whereas retroviruses have double-stranded DNA genomes. - (2) Common cold is sometimes caused by an adenovirus, whereas AIDS is caused by a retrovirus. - Which of the statement(s) given above is/are correct? - (a) 1 only - (b ) 2 only - (c) Both 1 and 2 - (d) Neither 1 nor 2 - **Answer: (b)** - **Approach:**Adenoviruses have double-stranded DNA genomes whereas retroviruses have single-stranded RNA genomes. - Genome simply refers to the complete set of genes in a cell or living thing. |

## Chromosomes:

- Every species has a fixed number of chromosomes, like 46 in humans.
- Eggs from the mother and sperm from the father together make the zygote.
- ![](https://ibiologia.com/wp-content/uploads/2019/07/main-qimg-d117bf6f5f9005251ca827be00f3561a-1.gif)
- The number of chromosomes in every nucleus of every cell of the body is fixed for all living organisms.
- All the cells of our body have 46 chromosomes, except the reproductive/sex cells/gametes which have only 23 pairs, so the resultant zygote continues with 46 chromosomes.

## Cell Division:

- Cell division is a continuous process that happens in all cells.
- There are two major kinds of cell division-Mitosis and Meiosis.

## Mitosis:

- Mitosis is the normal cell division where a cell divides to create two cells with the same number of chromosomes.
- This is seen when the process of normal growth and development happens in the body.

## Meiosis:

- This is a special process for creating reproductive cells(**gametes).**
- The result cells will have half the number of chromosomes.

## Haploid cell:

- Haploid refers to the presence of a single set of chromosomes in an organism’s cells.
- In humans, only the egg and sperm cells(gametes/sex cells) are haploid.
- Sexually reproducing organisms are diploid (having two sets of chromosomes, one from each parent).
- They contain half the number of chromosomes.
- They are represented as **n.**

## Diploid cells:

- They contain two sets of chromosomes or the complete set of chromosomes of an organism.
- **Somatic cells-**all the cells of organisms other than the gametes are diploid.
- They are represented as **2n.**
- **![](https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQaviwigfkuVnXg3OkkQUU9UG4VYo5X1fjI0xTnL1v4DTVqse5ly8sS6VYcvWC0juEKYwI&usqp=CAU)**
- Diploid is a term that refers to the presence of two complete sets of chromosomes in an organism’s cells, with each parent contributing a chromosome to each pair.
- Humans are diploid, and most of the body’s cells contain 23 chromosome pairs.
- One copy of each chromosome pair came from the individual's mother and the other from the individual's father.
- Since we have two copies of each chromosome, we also have two copies of every gene.

## Homologous chromosomes:

- They are a pair of similar chromosomes in length, shape, and gene position.
- One comes from the father and one from the mother.
- **For example-** Both parents will give the genes for a characteristic, say eye color.
- But we will not normally have cases where the child has both eyes with different colors (one of father and mother) eyes.

## INHERITANCE OF CHARACTERISTICS THROUGH MENDEL'S EXPERIMENTS (5:30 PM):

- Mendel began a series of experiments to find out how traits are passed from generation to generation.
- At the time, it was thought that parents’ traits were blended together in their progeny.
- All the characteristics in organisms are manifested in **two factors/genes/traits:**
- I. Dominant Trait
- II. Recessive Trait.
- These factors or genes are the units of inheritance.
- The dominant trait expresses itself in a way that overrides the impact of the recessive trait.
- The recessive trait cannot express itself in the presence of the dominant trait.
- **For example**- in the garden pea, the green color of the pod is dominant over the yellow color pod.
- We can get a yellow color offspring pod only if both parents are yellow.
- The traits that are dominant and which traits are recessive are determined by nature as per natural selection based on evolution.
- ![](http://ib.bioninja.com.au/_Media/mendels-pea-plants_med.jpeg)

## Homozygous:

- When both the genes are the same for a particular trait, for example- GG, YY.
- Where G is green and Y is yellow.

## Heterozygous:

-

- When both genes are different for a particular trait, for example- GY.

## Phenotype:

- The sum of an organism’s observable characteristics is its phenotype.
- While genotype is inherited from an organism’s parents, the phenotype is not.
- Environmental factors that may influence the phenotype include nutrition, temperature, humidity, and stress.
- **For example-**  Flamingos are naturally white in color, it is only the pigments in the organisms that they eat that cause them to turn vibrantly pink.

## Genotype

## :

- It is the subsequent combination of genes that an individual possesses for a specific gene.
- **For example**- A gene encodes eye color.
- In this example, the allele is either brown, or blue, with one inherited from the mother, and the other inherited from the father.
- The brown gene is dominant (B), and the blue allele is recessive (b).
- If the child inherits two different genes (heterozygous) then they will have brown eyes.
- For the child to have blue eyes, they must be homozygous for the blue-eye gene.
- ![](https://biologydictionary.net/wp-content/uploads/2020/12/genotypephenotype.jpg)

## UTILITY FOR BLOOD GROUP INHERITANCE (6:00 PM):

|  |  |
| --- | --- |
| Phenotype | Genotype |
| A | AA, AO |
| B | BB, BO |
| O | OO |
| AB | AB- Codominance where both the genes express themselves. |

- Both A and B are dominant over O.
- If both parents have the blood group A, the child can be O only if both the parents have AO AO, heterozygous groups.
- Such a correlation cannot be told for the Rhesus factor as per this concept.

|  |
| --- |
| Question 2:A married couple adopted a male child. A few years later, twin boys were born to them. The blood group of the couple is AB positive and O negative. The blood group of the three sons is A positive, B positive, and O positive. The blood group of the adopted son is: (a) O Positive  (b) A Positive  (c) B Positive  (d) Cannot be determined by the given data  Answer- (a)  As both A and B are dominant over O, their child cannot have an O blood group. |

## Sex determination:

- Humans typically develop as either male or female, depending on the combination of sex chromosomes that they inherit from their parents.
- The human sex chromosomes, called X and Y, are structures in human cells made up of tightly bound deoxyribonucleic acid, DNA, and proteins.
- ![](https://thumbs.dreamstime.com/b/sex-determination-vector-illustrator-computer-design-60818422.jpg)
- The phenotype ratio here is 1:1 as we see an equal number of sons and daughters.
- This means we have an equal probability of having a boy or a girl child.
- Humans who inherit two X chromosomes typically develop as females, while humans with one X and one Y chromosome typically develop as males.
- Hence, it can be said that the sex of the child is always determined by the genetic inheritance of the father, unlike the patriarchal norms that blame women for it.

## GENETIC ABNORMALITIES (6:45 PM):

- Genetic disorders occur when a mutation affects the genes of the baby or when the baby has the wrong amount of genetic material.

## Genetic disorders are classified on the basis of:

## I. The number of chromosomes:

## (a) Down Syndrome:

- It sees the presence of an extra chromosome called **Trisomy 21.**
- The child will have a total of 47 chromosomes.
- The child is born with a small round head, partially open mouth, and mental retrardation
- ![](https://www.hhmi.org/sites/default/files/News/2008/981432.gif)

## (b) Klinefelter’s syndrome

- XXY.

- The baby boy will have 47 chromosomes.
- This results in a male with the development of feminine characteristics.
- They are sterile in most cases.

## (c) Turner’s syndrome-

XO.

- It is a condition that affects only females when one of the X chromosomes (sex chromosomes) is missing.
- The girl will have only 45 chromosomes.
- She will be a reproductively sterile female.

## In-Vitro Fertilization :

- This process of embryo fertilization happens outside of the human body under monitored conditions.
- Mature eggs are retrieved from the ovaries and fertilized with sperm.
- After fertilization, the embryo(s)  is/are transferred to the uterus of another woman.
- The birth then happens normally.
- The baby will have no characteristics of the host woman, but only of the parents whose sperm and eggs were taken.
- ![](https://d2jx2rerrg6sh3.cloudfront.net/image-handler/picture/IVF%20process%20infographic%20-%20ectorPot%20_thumb_1.jpg)

## TWINS (7:15 PM):

## For identical (monozygotic) twins:

- The zygote can create a copy of itself.
- Hence the twins will have the same genetic material from both parents.

## For non-identical twins:

- Normally, one egg cell is produced per month.
- Sometimes, two egg cells can be produced, or even both ovaries produce an egg cell each.
- Two zygotes will be fertilized and they will be genetically different.
- They would be similar to two siblings born with a gap of some time.

## More examples of genetic defects/Autosomal diseases:

## Sickle Cell Anaemia:

- Anemia refers to the deficiency of iron or hemoglobin.
- When the Red Blood Cells(RBCs) become sickle-shaped, they are not able to hold a sufficient amount of hemoglobin.
- ![](data:image/jpeg;base64,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)
- This happens due to a defect in one gene present on one of the **autosomes** (one of the numbered chromosomes, as opposed to the sex chromosomes).
- Let the normal gene composition be HbHb and the diseased composition be Hb^sHb^s.
- We can have a heterozygous gene composition of the offspring as HbHb^s.
- In most cases, the defective gene effect is regressive, so the above-case offspring (HbHb^s) will be a normal person.
- This is because the normal gene Hb will dominate.
- So even if the defective gene is transferred in successive generations, they will not show the disease because the disease gene is recessive

## Marriage among siblings/close relatives:

- They can be **Carriers -**they can be normal themselves, but they can still carry the disease to the next generation.
- HbHb^s & HbHb^s can have offspring -Hb^sHb^s which will definitely have the disease.
- Such marriages can cause offspring with physical, and mental genetic defects.
- This is also the reason why small tribes who do not marry outside the tribe are more likely to have genetic abnormalities.

## SEX- CHROMOSOME-LINKED DISEASES (7:35 PM):

## Hemophilia:

- Hemophilia is a rare disorder in which the blood doesn't clot in a typical way because it doesn't have enough blood-clotting proteins.
- ![](https://my.clevelandclinic.org/-/scassets/Images/org/health/articles/14083-hemophilia)
- The British Royal family has this disorder.
- This disease is also a recessive disease.
- Normal- XX & XY.
- Let us assume the diseased female to be represented by X^hX^h.
- Let us assume the parents as XY & X^hX^h.
- Since this is a recessive disease,  the offspring will be either :
- **I.** XX^h (Normal/Carrier female child).
- **II.** X^hY( Diseased male child)
- For sex-linked diseases, either the man will be normal or he can be diseased, but he will never be a carrier.

## Color Blindness:

- The gene responsible for color blindness is located on the X chromosome.
- If a female inherits one normal color vision gene and one mutated gene, she won’t be red-green color blind, because it’s a recessive trait.
- But if she inherits two mutated color vision genes, she’ll be color-red-green blind.
- Since boys have only one X chromosome, their chance of inheriting red-green color blindness is much greater.
- Boys always inherit their X chromosome from their mother, so if the mom has red-green color blindness, or if the mom’s dad is red-green colorblind, her son will be too.
- Normal- XX, XY
- Disease X^hX^h, X^hY
- Normal carrier XX^h.
- |  |
  | --- |
  | **Question:** In the context of genetic disorders, consider the **following(Prelims 2009):**  - A woman suffers from color blindness while her husband does not suffer from it. - They have a son and a daughter. - In this context, which one of the following statements is most probably correct: - **(a).** Both children suffer from color blindness. - **(b).** The daughter suffers from color blindness, while the son does not. - **(c)** Both children suffer from color blindness. - **(d). The** Son suffers from color blindness while the daughter does not. - **Answer: (d)** - **Approach:** - Let the mother be X^cX^c (diseased) and the father be XY (healthy). - The offspring will be: - XX^c(daughter) , XX^c(daughter),  X^cY,(son) X^cY(son). |

## Ncerts for self-study:

- **Class 10-** Chapter 8
- **Class 12-** Chapters 4 & 5 (only basics).

## THE TOPICS FOR THE NEXT CLASS ARE

Biotechnology.