Chromosome for Grade 8

Chromosome for Grade 8. The Basic

1. Chromosome By: MNV BioScie

2. What is a Chromosome ? a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes. Chromosome means: chroma - colour ; some - body) First described by Strausberger in 1875. The term “Chromosome”, however was first used by Waldeyer in 1888.

3. Autosome An  autosome  is any chromosome that is not a sex chromosome. Each  autosome  stores many thousands genes, each of which performs a unique  function  in the organism's cells . 22 autosomes (chromosomes) Both identical both the two sexes.

4. Sex Chromosomes Sex chromosomes ( Gonosomes ) – Chromosomes involved in sex determination. 1 sex chromosome. Humans and most other mammals have two sex chromosomes, the X and the Y. Females have two X chromosomes in their cells, • Sperms have both X and a Y chromosomes • Egg cells all contain an X chromosome

5. C hromosome number Diploid cells (2N) where N- chromosome number have two. H omologous copies of each chromosome. The body cells of animals are diploid. Haploid cells (N) have only one copy of each chromosome. In animals, gametes (sperm and eggs) are haploid.

6. 2 parts: Chromatids: two identical parts of a chromosome Centromere: Joins chromatid together. • Primary Constriction

7. Telomere: A telomere is a region of repetitive DNA sequence at the end of chromosome. Protects the chromosome from deterioration of rom fusion with neighboring chromosomes. Each chromosome has two arms p (the shor t arm ) q (the long arm) .

8. Kinetochore A kinetochore is a protein structure that forms on a chromatid during cell division and allows it to attach to a spindle fiber on a chromosome. Its proteins also help to hold the sister chromatids together and play a role in

9. Karyotype A   karyotype  is simply a picture of a person's  chromosomes Two chromosomes specify sex, XX for female and XY for male. The rest are arranged in pairs, numbered 1 through 22, from largest to smallest.

10. Types of Chromosomes based on the position of Centromere Metacentric Chromosomes • The two arms are equal in length • Appears in ‘V’ shape. 2. Sub metacentric Chromosomes • Chromatids of one side are slightly longer than the other side • Resemble the letter ‘L’. 3. Acrocentric Chromosomes • Centromere is located closer to the end of chromatid • The small round structure is termed as satellite • Resemble the letter ‘J’ 4. Telocentric Chromosomes • Centromere at the end of chromosomes • Not seen in human cells • Resemble the letter ‘ i ’

11. Histone Histones  are a family of basic proteins that associate with DNA in the nucleus and help condense it into chromatin. His t o n e c a n b e g r oup e d into fi v e m a j or clas s e s : H1 / H 5 , H2A, H2B, H3, and H4 These are organized into two super-classes as follows: Core histones – H2A, H2B, H3 and H4 Linker histones – H1 and H5

12. A  nucleosome  is a section of DNA that is wrapped around a core of proteins. Inside the nucleus, DNA forms a complex with proteins called chromatin. Histones help in order to fit inside of the nucleus and take part in the formation of  chromosomes .

13. Chromatin Chromatin is a mass of genetic material composed of DNA and proteins that condense to form chromosomes.

14. DNA (deoxyribonucleic acid) the chemical inside the nucleus of a cell that carries the genetic instructions for making living organisms. The material inside the nucleus of cells that carries genetic information. GENE A gene is the functional and physical unit of heredity passed from parent to offspring. Genes are pieces of DNA, and most genes contain the information for making a specific protein