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Section 1: Human Inheritance

Explore the patterns of inheritance in humans, including single gene traits with multiple alleles and traits controlled by many genes. Understand the role of sex chromosomes in determining sex and other traits. Discover how genes interact with the environment to shape an organism's characteristics.

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Section 1: Human Inheritance

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  1. Section 1: Human Inheritance 7.2 A typical cell of any organism contains genetic instructions that specify its traits. Those traits may be modified by environmental influences. 7.2.c Students know an inherited trait can be determined by one or more genes.

  2. Patterns of Human Inheritance • A single gene can have more than two alleles • There is not always a one-to-one correspondence between trait and gene • Key concept: “Some human traits are controlled by single genes with two alleles, and other by single genes with multiple alleles. Still other traits are controlled by many genes that act together.” • What we discussed in chapter 5: single gene with 2 alleles

  3. Single Genes with Multiple Alleles • Multiple alleles- 3 or more forms of a gene that code for a single trait. • People carry only 2 alleles for each trait • Each chromosome carries one allele for each gene Blood type is determined by a single gene with three alleles. This chart shows which combinations of alleles result in each blood type.

  4. Traits Controlled by Many Genes • Some traits show a large number of phenotypes because the traits are controlled by multiple alleles (ex. Height) • Skin, eyes, hair color are also controlled by multiple alleles

  5. The Sex Chromosomes • Key concept: “The sex chromosomes carry genes that determine whether a person is male or female. They also carry genes that determine other traits.” • Sex chromosomes are one of the 23 pairs of chromosomes in a human body • Only chromosomes that sometimes don’t match Females have XX Males have XY

  6. Sex Linked Genes • Sex-linked Genes- genes on the X or Y chromosomes, these are passed from parent to offspring on the sex chromosome • Many of the genes on the X chromosomes are not on the Y chromosomes • Because males have only one X they are more likely to have a sex-linked gene than females

  7. Inheritance of Colorblindness • Red-green colorblindness is a sex-linked trait • If a girl receives only one recessive allele (written Xc) for red-green colorblindness she will not have the trait • If a boy receives one recessive allele he will be colorblind Carrier-person who has one recessive allele for a trait and one dominant

  8. Colorblindness What sex is the person that is a carrier for colorblindness?

  9. The Effect of Environment • Key concept: “Many of an organism’s characteristics are determined by an interaction between genes and the environment.” • A diet lacking in protein, minerals, vitamins, … can affect growth

  10. Section 1: Human Inheritance • What are some patterns of inheritance in humans? • What are the functions of the sex chromosomes? • What is the relationship between genes and the environment?

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