Genetics and Inheritance Year 10 Biology Part 1: Genes & Chromosomes

The Genetic code  Features/ traits are inherited in the form of a genetic code. (passed from one generation to the next)  This code is written in a molecule called deoxyribonucleic acid (DNA)  Genes are segments or sequences of DNA that code for a particular trait/ characteristic 2. Genes are passed on from one generation to the next! Each genetic instruction that codes for a particular trait (shape of ear lobe, blood group or eye colour) is called a gene.

Genes are inherited  Meiosis produces sex cells/gametes: ova and sperm.  Results in the chromosome number being halved.  Genetic information received from your mother – Maternal chromosomes  Genetic information received from your father – Paternal chromosomes 3. Genes are passed on from one generation to the next!

 Fertilisation occurs when gametes from the mother and father unite to produce a zygote. Cell division:  Meiosis produces 4 haploid daughter cells: sex cells/ gametes -half chromosome number  Mitosis produces 2 daughter cells: body cells/ somatic cells – full chromosome number 4. Genes are passed on from one generation to the next!

Genes are inherited from each parent as your genotype! 5. Genes are passed on from one generation to the next!  This double set of genetic instructions (one set from each parent) makes up your genotype (your set of genes).  The visible expression of the genotype as a particular trait or feature is called the phenotype.  The phenotype may also be influenced by your environment Phenotype: (What you look like) physical appearance due to your genotype and environmental factors Genotype: (what your made of) Your genetic instructions from each parent

Chromosomes can be Autosomes or Sex Chromosomes 6. Genes are passed on from one generation to the next!  Somatic cells have 23 pairs of chromosomes, numbered 1-23 depending of size.  22 pairs of autosomes  1 pair of sex chromosomes Males have XY Females have XX

7. Genes are passed on from one generation to the next!

Chromosomes can be Homologous or Non-homologous pairs 8. Genes are passed on from one generation to the next!

Human Karyotype Homologous Chromosomes 9. Genes are passed on from one generation to the next!  Scientists construct a karyotype:  To test for gender  To test for chromosomal disorders Cells about to divide are treated and stained, mounted on slides for viewing and are photographed. Photographs are cut up and arranged into pictures that show chromosomes in matching pairs (homologous chromosomes) in order from smallest to largest

Chromosomal Disorders 10. Genes are passed on from one generation to the next!

Genes make you YOU! GENES:  Determine who you are, determine many of the traits and characteristics that make you, YOU.  A segment of double-stranded DNA that contains information that codes for the production of a particular protein or function.  Are located on specific chromosomes,  We have 20000–24000 within our cells.  Can be found at a specific locus on a specific chromosome  Are linked to genes on the same chromosome.  The total set of genes in an organism is its genome  A genome map: describe the order of genes and the spacing between them on each chromosome 11. Genes are passed on from one generation to the next!

12. Genes are passed on from one generation to the next!

Genomes 13. Genes are passed on from one generation to the next! Genome size is described in base pairs (bp)

14. Genes are passed on from one generation to the next!

Sequencing The Human Genome 15. Genes are passed on from one generation to the next!  Identifies the order of nucleotides along a gene.  DNA sequencers use four different coloured fluorescent dyes (each binding to A, T, C or G in DNA)  identify the nucleotide sequence as it builds a complementary copy to the DNA template sample provided.  An example of the output of a DNA sequencer is shown at left.

 Required to map the human genome (total set of genes)  To describe the order of genes and the spacing between them on each chromosome.  The Human Genome map revealed/ confirmed:  Similar regulatory genes between species (We even share similarities with the fruit fly!)  Parts of our genome are virtually interchangeable with our close primate ‘cousins’ 16. Genes are passed on from one generation to the next! Sequencing The Human Genome

17. Genes are passed on from one generation to the next!