bio h genetics (mendelian and non mendelian)

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19 Terms

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Human body cells have ….
44 autosomes and 2 sex chromosomes
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males sex chromosome
XY
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female sex chromosome
XX
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GAMETES
* are sex cells (22 auto 1 sex chromosome)
* Female gamete- egg cell
* Male gamete- sperm cell
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Pedigree (family tree of disease)
* A pedigree chart shows relationships within a family and shows how traits are passed from one generation to the next. 
* Genetic counselors can use a pedigree to infer the genotype of family members. 
* A pedigree chart shows relationships within a family and shows how traits are passed from one generation to the next. 
* Genetic counselors can use a pedigree to infer the genotype of family members. 
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Genetics
The study of how hereditary info is passed from parents to offspring
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Genes 
* DNA code for trait 
* Ex. eye color

Your genes come in pairs (one from mom and one from dad)

That pair is an **allele**
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Alleles
* Variation of traits 
* Ex. Blue eyes, green eyes, brown eyes
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Probability
Chances of inheriting a particular allele
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**Genotype**
* **Genes**
* **Homozygous, heterozygous, dominant recessive** 
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**Phenotypes**
* **Physical traits**
* **Tall, short, green seeds, yellow seeds**
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**Law of Dominance**
* **Organsism have 2 copies of every gene**
* **1 from mom and 1 from dad**
* **Sometimes those genes are for different alleles**
* **Moms allele from blue eyes and Dads allele for brown eyes**
* dominant will override recessive (unless dominant isn’t present, like in homozygous recessive)
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**Law of segregation**
* **As the parent cell (p generation) prepares to make gametes (egg or sperM), it undergoes meiosis**
* **During meiosis, the 2 alleles segregate so that each gamete cell will have only 1 copy of each gene**
* **The law of segregation states that the movement of alleles into daughter cells is RANDOM**
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**Incomplete Dominance**
* **every genotype has its own phenotype (one allele is not completely dominant over the other) the resulting phenotype is a blending of the parental traits. (two alleles produce 3 phenotypes.)**
* **Heterozygous phenotype is somewhere in between homozygous phenotype (ex. red plus white is PINK not RED AND WHITE)**
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**Codominance**
* **both alleles are independently and equally expressed in the heterozygote. Examples include**
* Roan (stippled red and white) coat color in cattle. A cross between a red bull and a white cow produces all roan offspring
* ABO human blood groups
* __**Blood types are codominant**__ 
* In a  cross between two heterozygous (roan) shorthorn cattle, red, roan, and white offspring are produced in a 1:2:1 ratio
* __**red + white= red and white not PINK**__
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**Multiple alleles in blood**
* **The 4 common blood groups of the human ABO blood group system are determined by three alleles Ia, Ib, and i (also represented in some texts as A, B, and O)**
* **ABO antigens consist of sugars attached to the red blood cell surface. These sugars provide individual antigenic properties. The alleles code for enzymes that join these sugars together.** 
* **Allele i produces a non-functional enzyme that is unable to make changes to the basic antigen (sugar) molecule**
* **The other two alleles (IA, IB) each produce a different enzyme that adds a different specific sugar to the basic antigen.** 


* **Any one individual possesses only two alleles and they are expressed equally.** 
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**Sex Linkage**
* **phenotypic expression of an allele that is dependent on the sex of the individual and is directly tied to the sex chromosomes**
* **Most sex-linked genes are present on the X chromosome (x linkage) and have no corresponding allele on the smaller male chromosome**
* **In some cases, a phenotypic trait is determined by an allele on the Y- chromosome. Because the Y chromosome is small and does not contain many genes, few traits are - y-linked, and Y- linked diseases are rare.** 
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**Sex Linkage (pt. 2)**
* **Sex-linked traits show a distinct pattern of inheritance**
* **Fathers pass sex-linked alleles to all their daughters but not to their sons**
* **Mothers can pass sex inked alleles to both sons and daughters**
* **In females, sex-liked recessive traits will be expressed only in the homozygous condition**
* **In contrast, any male receiving the recessive allele from his mother will express the trait.**
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**Sex-linked Dom Inheritance**
* **Sex-linked dom inheritance is rarer because all daughters of affected males will be affected (the heterozygous condition is not a carrier)**
* **Sex-linked dominant traits are never passed from father to son**
* **Affective females produce 50% normal 50% affected offspring**