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Beschreibung
Karteikarten von Chelsi Souch, aktualisiert more than 1 year ago
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Erstellt von Chelsi Souch
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| Frage | Antworten |
| Heredity | transmission of traits |
| Genetics | scientific study of heredity |
| Mendel created | - purebred (what does that mean?) varieties of pea plants and – crossed two different purebred varieties. |
| Hybrids | are the offspring of two different purebred varieties. – The parental plants are the P generation. – Their hybrid offspring are the F1 generation. – A cross between the F1 plants forms the F2 generation. – F stands for “filial” |
| character | heritable feature that varies among individuals |
| A trait | variant of a character. |
| The seven characters studied by Mendel | |
| Tracking one character (flower color) | |
| Mendel’s four hypotheses (1 & 2) | 1. The alternative versions of genes are called alleles (previously termed traits). Example: Gene for flower color - P allele = purple color - p allele = white color 2. For each inherited character, an organism inherits two alleles, one from each parent. – An organism is homozygous (pure breeding or true breeding) for that gene if both alleles are identical. – An organism is heterozygous for that gene if the alleles are different (Hybrid). – Example: Flower color (P = purple; p = white) » PP and pp = homozygous » Pp = heterozygous |
| Mendel’s four hypotheses (3 & 4) | 3. If two alleles of an inherited pair differ, – then one determines the organism’ s appearance is called the dominant allele and – the other has no noticeable effect on the organism’ s appearance and is called the recessive allele. – Example: Flower color in pea plants » P = dominant allele (purple color) » p = recessive allele (white color) » PP and Pp = purple flower; pp = white flower 4. Gametes (haploid) carry only one allele for each inherited character. – The two alleles for a character segregate (separate) from each inherited character. – The two alleles for a character segregate (separate) from each other during the production of gametes. – This statement is called the law of segregation. – Example: Flower color (P = purple; p = white) » PP parent produces only P gametes » Pp parent produces P or p gametes » pp parent produces only p gametes |
| 1. Mendel’s Law of Segregation | That organisms have two genetic elements which separate when gametes are formed. The fusion of gametes at fertilization pairs these elements once again Occurs during meiosis I: homologous chromosomes separation in anaphase I |
| 2. Mendel’s Law of Independent Assortment | Factors for different characteristics (different gene pairs) are inherited independently from one another Occurs during meiosis I: Independent assortment of homologous chromosomes in metaphase 1 |
| What is a Dihybrid cross? | |
| Incomplete dominance | MANY ALLELES SHOW INCOMPLETE DOMINANCE In monohybrid crosses in some cases outcome was different Ex 1. SNAPDRAGONS (red X white = PINK) |
| Codominance | Both alleles express together in the heterozygotes |
| Epistasis | One gene may alter the effect of (expression) of another gene Ex 1. Mice have TWO GENES fur coat colour B and C B = BLACK b = brown C = COLOUR If cc (homozygous recessive) is present the mouse will be white regardless of which B gene it has One gene may alter the effect of (expression)of another gene |
| Environment | Can modify the expression of the gene Coat colour of animals Can modify the expression of the gene |
| Polygeneic inheritance | Most characteristics are determined more than one gene Height and Skin color |
| Pleiotropy and sickle cell disease | – Pleiotropy is when one gene influences several characters. – Sickle-cell disease exhibits pleiotropy • results in abnormal hemoglobin proteins, and causes disk-shaped red blood cells to deform into a sickle shape with jagged edges. • causes multiple symptoms: weakness, pain, organ damage and paralysis |
| Multiple alleles | Many genes have more than two alleles in the population – In a population Multiple alleles often exist for a characteristic |
| Human ABO blood groups are an example of multiple alleles and codominance | Blood cells have either A or B type surface carbohydrates, or none (O) • The immune system produces blood proteins called antibodies that bind to foreign carbohydrates. • If a donor’ s blood cells have a carbohydrate (A or B) that is foreign to the recipient, the blood cells may clump together, potentially killing the recipient. – The clumping reaction is the basis of a blood-typing lab test. – The human blood type alleles IA and IB are codominant, with both alleles expressed in heterozygous individuals who have type AB blood. |
| Multiple alleles for the ABO blood groups | Alleles are alternative forms of a gene that arose by mutation. Each gene (100s or 1000s of base pairs long) can have multiple alleles. |
| Sex chromosomes and sex-linked genes | Sex chromosomes influence the inheritance of certain traits. Human sex chromosomes: XX = female; XY = male |
| genetic abnormality | rare version of an inherited trait |
| genetic disorder | nherited condition that causes medical problems |
| Inheritance patterns in humans are often studied by | tracking inheritance patterns of genetic disorders through generations |
| Pedigree | is a chart showing the pattern of inheritance of a trait in a family |
| Syndrome | The set of symptoms that characterize a genetic disorder |
| Any gene located on a sex chromosome is called | sex-linked gene. • Most sex-linked genes are found on the X chromosome. • Red-green colorblindness is a common human sex-linked disorder and caused by a malfunction of light-sensitive cells in the eyes |
| Sex-linked traits | |
| HYPERTRICHOSIS | Severe hypertrichosis is quite rare, almost certainly due to unknown genetic defects, and can result in excessive or animal-like hair on both face and body. Unfortunately, some of these people have been displayed in carnival sideshows with names such as "dog-boy" or the "bearded lady." |
| Linked genes | Linked genes are located close together on a chromosome and tend to be inherited together. – Thomas Hunt Morgan (early 1900s) • used the fruit fly Drosophila melanogaster and • determined that some genes were linked based on the inheritance patterns of their traits. • Example: Body color gene and wing length gene are linked |
| Genetic recombination: crossing over | Crossing over can – separate linked alleles, – produce recombinant gametes with new combinations of alleles, and – produce offspring with recombinant phenotypes. • The percentage of recombinant offspring among the total is called the recombination frequency. Crossing over can produce recombinant gametes |
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