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Genetics

Chapter 2 Science 30. Genetics. What is genetics?. Genetics is the study of how traits are passed from parent to offspring Nucleus of cells contain genetic material organized into chromosomes. Chromosomes carry genes, units of hereditary. Each chromosome contains many different genes.

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Genetics

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  1. Chapter 2 Science 30 Genetics

  2. What is genetics? • Genetics is the study of how traits are passed from parent to offspring • Nucleus of cells contain genetic material organized into chromosomes. • Chromosomes carry genes, units of hereditary. • Each chromosome contains many different genes. • Humans have 23 pairs of chromosomes (46 total). • 1 set from each parent.

  3. Chromosomes • Long, thin coiled strands of DNA • Seen during cell division. • X shape is created when copies attach at one point (centromere). BrainPop - DNA

  4. Genes • A segment of DNA that codes for a specific protein. • The order of the bases codes for a specific trait (e.g.. Tongue rolling). • Some genes are dominant and some are recessive. Free ear lobe a.) is dominant to attached ear lobe b.).

  5. Role of proteins • Each gene makes a protein…these are used for/as: • Enzymes (amylase- digestion). • Structural (Keratin/ collagen). • Transport ( cell membranes). • Hormones (insulin). • Defense (antibodies). • Energy (Casein). • Muscle contraction (Actin and myosin). BrainPop - RNA

  6. Human karyotype • All 23 chromosomes matched to their pair is a called a karyotype. • 3 features are used to identify pairs: • Length of chromosome (longest = #1) • Pattern of dark bands on chromosome. • Position of centre connection (centromere). • The last 2 chromosomes are the sex chromosomes: • XX = female. • XY= male

  7. Amniocentesis • Prenatal test done to determine karyotype fetus • Taken during week 15 – 16 of pregnancy • Used to diagnose genetic abnormalities such as a trisomy (3 copies of a single chromosome)

  8. Trisomy • Trisomy 21 – Down Syndrome • Trisomy 18 – Edward’s Syndrome • Trisomy 13 – Patau Syndrome • XXY – Klinefelter Syndrome

  9. Down Syndrome (21) • Results in: • Delayed physical growth • Lowered cognitive ability • Congenital heart disease in 50% of individuals • Most common autosomal trisomy

  10. Edward’s Syndrome (18) • Results in : • Kidney and heart malformations • Developmental delays • Cleft lip and palate • Protruding intestines • Second most common autosomal trisomy

  11. Patau Syndrome (13) • Results in: • Developmental delays • Heart and kidney defects • Polydactalism • Cleft lip and palate • Malformed genitalia

  12. Klinefelter Syndrome (XXY) • Small children may have reduced muscular development and strength • Symptoms may not be visible until the on-set of puberty • Individuals may have breast development due to reduced levels of testosterone.

  13. Chromosome Replication • The 2 ways that an exact copy of the DNA from the chromosome is created are: • Mitosis: • occurs in somatic/ autosomal (body cells) • Asexual reproduction • Meiosis: • Occurs in germ cells (in ovaries and testes) • Produces gametes (egg and sperm) for sexual reproduction

  14. Mitosis • Body cells (autosomal cells) divide by replicating all the parts and dividing into 2 identical cells • 1 parent cell = 2 identical daughter cells • A copy of the DNA must be made before replication; each strand replicates and attaches at a centre point (centromere). • Parent cell is diploid; 2n(2 copies of each chromosome • Daughter cells are diploid; 2n (2 copies of each chromosome)

  15. Summary of Mitosis: BrainPop - Mitosis

  16. Meiosis • Occurs in germ cells to produce gametes (egg or sperm) • Germ cell replicates DNA and divides twice • 1 parent cell = 4 sex cells • Parent cell is diploid; 2n (2 copies of each chromosome) • Sex cell is haploid; 1n (1 copy of each chromosome)

  17. Summary of Meiosis:

  18. Fertilization • The sperm and the egg (gametes) are each haploid, the fertilized egg (zygote) is diploid and can reproduce through mitosis. • This increases variation and allows for more than 70 trillion gene combinations. • Crossing over improves the variation possible in the gametes; explains why 2 siblings look so different. BrainPop - Gender Determination

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