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1.What are chromosomes composed of? 2.Where do we find chromosomes? Objectives: –Discuss sex-linked traits 5-17.

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Presentation on theme: "1.What are chromosomes composed of? 2.Where do we find chromosomes? Objectives: –Discuss sex-linked traits 5-17."— Presentation transcript:

1 1.What are chromosomes composed of? 2.Where do we find chromosomes? Objectives: –Discuss sex-linked traits 5-17

2 Unit # 9 Chromosomes and Inheritance Book Chapter 12 My.hrw.com

3 Morgans Experiments For fruit flies red eyes = normal Morgan found a male with white eyes white eyed male X red eyed female all F 1 were red eyed … so red = dominant F 1 X F 1 3 red eyed to 1 white eyed BUT all white eyed flies were males – EXPLAIN!

4 XrXr Y XRXR XRXR XRXR XrXr XRXR XrXr XRXR Y XRXR Y Original cross: white eyed male X red eyed female

5 XRXR Y XRXR XrXr XrXr XRXR XRXR XRXR XrXr Y XRXR Y F 1 X F 1

6 Review: Sex chromosomes – X and Y – chromosomes that contain genes that determine sex (along with other traits)Sex chromosomes – X and Y – chromosomes that contain genes that determine sex (along with other traits) Autosomes – all other chromosomes and the genes they carryAutosomes – all other chromosomes and the genes they carry

7 Sex-linked traits –Sex-linked traits – traits that are coded by an allele on a sex chromosome –Why are there more X sex linked traits? X chromosome is bigger than the y chromosomeX chromosome is bigger than the y chromosome

8 Previewing Assignment: Read 12.1 and answer #s 1-3, 6-9 on the bottom of page 240 – DUE Wednesday 5-18 5-16

9 Linked genes – genes that tend to be inherited togetherLinked genes – genes that tend to be inherited together Usually means they are on the same chromosomeUsually means they are on the same chromosome

10 Using what you learned yesterday about eye color for fruit flies cross a white-eyed female with a red eyed male and determine the geno and phenotypic ratios. 5-11 XRXR Y XrXr XrXr XRXR XRXR XrXr XrXr XrXr XrXr Y Y 50% red eyed females X r X R and 50% white eyed males X r Y

11 Germ-cell mutation – mutations in organisms gametes – do not affect the organism itself but can affect its offspringGerm-cell mutation – mutations in organisms gametes – do not affect the organism itself but can affect its offspring Somatic cells – organisms body cellsSomatic cells – organisms body cells Somatic-cell mutation – mutations that occur in organisms body cellsSomatic-cell mutation – mutations that occur in organisms body cells Lethal Mutations – mutations causing death (mostly before birth) – Some mutations beneficial leads to natural selectionLethal Mutations – mutations causing death (mostly before birth) – Some mutations beneficial leads to natural selection

12 Chromosomal mutations = mutations involving changes in chromosome structure or number Deletion – loss of a piece of a chromosome (it breaks off)Deletion – loss of a piece of a chromosome (it breaks off) Inversion – chromosome part breaks off and reattaches backwardsInversion – chromosome part breaks off and reattaches backwards Translocation – piece of chromosome breaks off and reattaches to a non- homologous chromosomeTranslocation – piece of chromosome breaks off and reattaches to a non- homologous chromosome

13 Nondisjunction – chromosomes failing to separate during meiosisNondisjunction – chromosomes failing to separate during meiosis Get too many, or too few chromosomes (Trisomy 21 = Down syndrome)Get too many, or too few chromosomes (Trisomy 21 = Down syndrome) –Review trisomy and monosomy aneuploidy – having an abnormal number of chromsomesaneuploidy – having an abnormal number of chromsomes

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15 Point Mutation –Point Mutation – –substitution, addition or removal of a single nucleotide in DNA Substitution –Substitution – –when one nucleotide replaces another Gene mutations = changes in the DNA sequence that makes up a gene

16 Substitution –Substitution – –when one nucleotide replaces another Insertion Mutation –Insertion Mutation – –one or more nucleotide are added to a gene (can lead to a frame-shift mutation) Frame-shift Mutation –Frame-shift Mutation – –Deletion or addition of a nucleotide(s), shifting all the codons, changing all the amino acids

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18 Pedigree – diagram that shows how a trait is inherited over several generations

19 XrXr Y XRXR XRXR XRXR Y XRXR XrXr Original cross: white eyed male X red eyed female F 1 X F 1


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