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6.1 Human Inheritance

6.1 Human Inheritance. Patterns of Human Inheritance. Mendel studied traits that were controlled by genes with one dominant allele and one recessive allele. The inheritance of traits is rarely this simple.

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6.1 Human Inheritance

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  1. 6.1 Human Inheritance

  2. Patterns of Human Inheritance Mendel studied traits that were controlled by genes with one dominant allele and one recessive allele. The inheritance of traits is rarely this simple. Some human traits are controlled by single genes with two alleles, and others by single genes with multiple alleles. Still other traits are controlled by many genes that act together.

  3. Single Genes With Two Alleles Free or attached earlobes A widow’s peak If both parents have heterozygous alleles, the probability of the offspring having that trait is 75%.

  4. Single Genes with Multiple Alleles Multiple alleles : Some traits are controlled by a single gene that has more than two alleles – three or more forms of a gene that code for a single trait Ex. Blood type : A, B, AB, or O A, B are codominant. Type O is recessive.

  5. Traits controlled by Many Genes Some human traits show a large number of phenotypes because the traits are controlled by many genes. The genes act together as a group to produce a single trait. At least 4 genes control height in humans. Skin, eye, and hair color are other traits that are controlled by multiple genes.

  6. The Sex Chromosomes The sex chromosomes are one of the 23 pairs of chromosomes in each body cell. The sex chromosomes carry genes that determine whether a person is male or female. They also carry genes that determine other traits.

  7. The Sex Chromosomes Girl or Boy? The sex chromosomes are the only chromosome pairs that do not always match Girls : XX match Boys : XY do not match Sex Chromosomes and Fertilization Mother : XX, Father XY 4 possibilities : XX, XX, XY, and XY 50% chance of a girl and 50% chance of a boy.

  8. Sex Linked Genes Genes on the X and Y chromosomes are often called sex-linked genes because their alleles are passed from parent to child on a sex chromosome. These traits are called the sex-linked traits. EX: Colorblindness

  9. Can you see the number in the circle?

  10. What shape do you see here?

  11. Inheritance of Colorblindness Colorblindness is a trait controlled by a recessive allele on the X chromosome. Carrier: a person who has one recessive allele for a trait and one dominant allele. Higher chance for boys to receive the colorblind gene than girls.

  12. Can you recognize what it says here?

  13. Previous slide : “NO” • What bothers colorblind people most?- When grilling a piece of meat, a red deficient individual cannot tell whether it is raw or well done. Many cannot tell the difference between green and ripe tomatoes or between ketchup and chocolate syrup! Many others are always buying and biting into unripe bananas - they cannot tell if they are yellow or green, and the matt, natural material makes it even harder to distinguish.- Some food may look definitely disgusting to color vision deficient individuals: a plate full of spinach, for instance, just appears to them like cow pat.

  14. - They can however distinguish some citrus fruits. Oranges seem to be of a brighter yellow than that of lemons.- A colorblind person is generally unable to interpret the chemical testing kits for swimming pool water, test strips for hard water, soil or water pH tests because they rely on subtle color differences.- Many colorblind people cannot tell whether a woman is wearing lipstick or not. More difficult to handle for some is the inability to make the difference between a blue-eyed blonde and a green-eyed redhead.- Color vision deficiencies bother affected children from the earliest years. At school, coloring can become a difficulty when one has to take the blue crayon - and not the pink one - to color the ocean.- Bi-color and tri-color LEDs (Light Emitting Diodes): is that glowing indicator light red, yellow, or green? Same problem with the traffic lights...

  15. The Effect of Environment Many of an organism’s characteristics are determined by an interaction between genes and the environment. People’s heights are controlled by several genes, but also controlled by the diet. A good muscle coordination might help you to play a musical instrument, but you still have to practice.

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