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Inheritance

Inheritance. Why are you unique?. Inheritance. What we are like depends on the genes we inherit from our parents The study of inheriting characteristics is called genetics. Menu page. choose the section you want to work on from this page. What is Variation?.

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Inheritance

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  1. Inheritance Why are you unique?

  2. Inheritance • What we are like depends on the genes we inherit from our parents • The study of inheriting characteristics is called genetics

  3. Menu page choose the section you want to work on from this page

  4. What is Variation? • Individuals within a species have different characteristics • Variation ensures survival

  5. Two types of variation 1. discontinuous • A characteristic you either have or you don’t!

  6. Two types of variation 2. Continuous • Produces a range of differences for a single characteristic within a population • Variation in height is an example of this…

  7. Sexual reproduction Asexual reproduction needs only one parent produces identical offspring called clones Does variation always happen? • needs two parents • produces offspring with a mixture of their characteristics

  8. What can you remember so far? • Click the brain box picture to check your knowledge and understanding • Or go back to the start again if you need to look at the information again ……

  9. About cells • Dividing and growing!

  10. Cell division • Cells divide to make new cells • Cells divide when we are growing • Cells divide during repair of the body • Cells divide to make eggs and sperms

  11. Cell division by mitosis • Mitosis is cell division of body cells • Mitosis produces 4 exact copies of the parent cell • The new daughter cells have the diploid number of chromosomes

  12. Cell division by meiosis • Meiosis produces sex cells or gametes • Sex cells have half, the haploid number, of chromosomes

  13. How many chromosomes? • Humans have 23 pairs of chromosomes like these • The diploid number of chromosomes is 23x2 = 46 • Sex cells (gametes) have 23 single chromosomes - the haploid (half) number

  14. What’s the point? • An egg cell has 23 chromosomes • A sperm cell has 23 chromosomes • When they join at fertilisation there are 46 chromosomes • This makes a full set of instructions to make a new human being!

  15. What can you remember so far? • Click the brain box picture to check your knowledge and understanding • Click here to do a worksheet • Click here to try another worksheet • Or go back to the start again if you need to look at this information again …… • Or back to the main menu

  16. Boys or girls? • What will your baby be?

  17. What are little girls made of? • XX

  18. What are little boys made of? • XY

  19. Predicting the chances: • Will it be a boy? • Will it be a girl? • We can work out the chances….

  20. Mums and Dads! Now work it out! • Mums produce only and chromosomes • Dads produce or chromosomes x x x x x x x x x x Y x Y x Y Y

  21. …and the babies? • Half will be girls • Half will be boys! • 50% of each sex

  22. What can you remember? • Try out the worksheet exercise… • Or go back to review what you have learnt • Or return to the main menu

  23. Why am I unique? • It’s down to your genes!

  24. It’s all down to your parents! • At fertilisation two gametes join • A gamete has half a set of instructions – the haploid number • A zygote is a fertilised egg cell • It has has a full set of instructions - the diploid number

  25. What causes variation?

  26. What is a gene? Adenine Thymine Guanine Cytosine • Genes are short sections of chromosomes • Genes are groups of bases on DNA molecules • All genes are made of just 4 bases

  27. Pairs of bases! A – T G – C T – A C - G • The four bases are arranged in pairs on chromosomes • A always pairs with T • C always pairs with G

  28. Amazing spirals • The arrangement of bases forms a double helix shape – like a twisted ladder! • This is a chromosome

  29. So why do you look like that??

  30. Phenotype • The physical appearance of individuals within a species varies • The genes that are inherited from parents control the phenotype of each individual

  31. Genotype • The different genes that each individual has is their genotype • Every body cell carries pairs of genes on the paired chromosomes • Genes can be dominant or recessive

  32. What have you learnt from this section? • Test yourself here • Or go back and look at this section again • Or select a new topic from the menu

  33. So how do your genes work?

  34. Gene competitions? • This rabbit’s genotype is BB – the black fur gene isdominant This rabbit’s genotype is bb – the white fur gene is recessive

  35. How do the genes work? Homozygous - two genes the same Heterozygous - two different alleles Homozygous BB? Bb? bb?

  36. How do they work? • Dominant genes are ‘stronger’ • They are written as capital letters -‘B’ • Recessive genes are ‘weaker’ • They are written as small letters – ‘b’ This rabbit may have a genotype of either Bb or BB

  37. Genes in conflict? • B + B =BB • B + b = Bb • b + b = bb Phenotype - Black fur Genotype BB Phenotype - Black fur Genotype - Bb Phenotype - White fur Genotype - bb

  38. Now work it out….. B B B B B B parent B b b B b b b parent b b B b B b b gametes offspring

  39. All the offspring have the same genotype They all have one dominant gene They all have one recessive gene The dominant gene ‘wins’ so the offspring all have black fur! What are the off spring like? B b B b

  40. What is their genotype? • Offspring have a mixture of their parents’ genes: • They are heterozygous • They each have one allele for white fur and one allele for black fur B b

  41. What about the next generation? B B b B b b B B B B b B B b B b b b b b parents gametes 3 : 1 offspring

  42. What are their genotypes? heterozygous B b B B homozygous b b homozygous

  43. Got it? Test your self here Or go back and have another look at the facts first! Or back to the main menu. Teachers can use the extra resource Punnet Squares on an IWB but you may need to download Smartbook software [free of charge] to use the file –

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