S6) Genotype, Phenotype, Inheritance Flashcards
What is a pedigree chart?
A pedigree is a diagram showing genetic information from a family, using standardized symbols
![](https://s3.amazonaws.com/brainscape-prod/system/cm/513/239/465/a_image_thumb.jpg?1509204387)
State 2 purposes of a pedigree chart
- Determines whether the pattern of inheritance for a given trait
- Discovers whether the gene in question is located on an X or Y chromosome or an autosome
Why is it important to establish how a trait is inherited?
State 3 reasons
If the pattern of inheritance can be established, it can be used to predict genetic risk in several situations, including:
- Pregnancy outcomes
- Adult-onset disorders
- Recurrence risks in future off spring
Pedigrees use a standardised set of symbols.
How are males and females represented?
- Squares represent males
- Circles represent females
![](https://s3.amazonaws.com/brainscape-prod/system/cm/513/239/475/a_image_thumb.png?1509211286)
Pedigrees use a standardised set of symbols.
How are affected individuals represented?
Individuals with the phenotype in question is represented by a filled-in symbol
![](https://s3.amazonaws.com/brainscape-prod/system/cm/513/239/477/a_image_thumb.png?1509211369)
Pedigrees use a standardised set of symbols.
How are heterozygotes represented?
Heterozygotes, when identifiable, are indicated by a shaded dot or a half-filled symbol
![](https://s3.amazonaws.com/brainscape-prod/system/cm/513/239/481/a_image_thumb.png?1509211427)
Pedigrees use a standardised set of symbols.
How are individuals represented when their sex is unknown?
If the sex of a person is unknown, a diamond is used
![](https://s3.amazonaws.com/brainscape-prod/system/cm/513/239/484/a_image_thumb.png?1509211498)
Pedigrees use a standardised set of symbols.
How are romantic relationships represented?
- Parents are connected by a horizontal line
- Closely related parents (such as first cousins) are connected by a double line
- Divorced parents are connected by a horizontal line with slanted lines
![](https://s3.amazonaws.com/brainscape-prod/system/cm/513/239/487/a_image_thumb.png?1509211852)
Pedigrees used a standardised set of symbols.
How are offspring represented?
- Offspring are connected to parents by a vertical line
- Off spring are connected by a horizontal sibship line (listed in birth order from left to right)
![](https://s3.amazonaws.com/brainscape-prod/system/cm/513/239/492/a_image_thumb.png?1509212064)
Pedigrees used a standardised set of symbols.
How are twins represented?
- Non-identical twins are connected by two diagonal lines
- Identical twins are connected by two diagonal lines as well as a horizontal sibship line
![](https://s3.amazonaws.com/brainscape-prod/system/cm/513/239/494/a_image_thumb.png?1509211933)
Pedigrees used a standardised set of symbols.
How are aborted, miscarried or stillborn offspring represented?
Deceased offspring are represented with a cross through their respective symbols
![](https://s3.amazonaws.com/brainscape-prod/system/cm/513/239/495/a_image_thumb.png?1509212227)
Pedigrees used a standardised set of symbols.
How are deceased individuals represented?
Deceased individuals are represented with a diagonal line through their respective symbol
![](https://s3.amazonaws.com/brainscape-prod/system/cm/513/239/497/a_image_thumb.png?1509212289)
Explain the numbering system in pedigree construction
- Each generation is identified by a Roman numeral (I, II, III, and so on)
- Each individual within a generation is identified by an Arabic number (1,2,3, and so on)
![](https://s3.amazonaws.com/brainscape-prod/system/cm/513/239/499/a_image_thumb.png?1509211087)
What are the five basic Mendelian patterns of inheritance for traits controlled by single genes?
- Autosomal recessive inheritance
- Autosomal dominant inheritance
- X-linked dominant inheritance
- X-linked recessive inheritance
- Y-linked inheritance
Identify a non-Mendelian pattern of inheritance
Mitochondrial inheritance - traits controlled by single genes coded for by mitochondrial genes
![](https://s3.amazonaws.com/brainscape-prod/system/cm/513/239/502/a_image_thumb.jpg?1509204801)
Identify 3 unique features of autosomal recessive inheritance
![](https://s3.amazonaws.com/brainscape-prod/system/cm/513/239/505/q_image_thumb.jpg?1509205459)
- All the children of two affected (homozygous) individuals are affected
- The risk of an affected child from two heterozygote parents is 25%
- For rare traits, affected individuals have unaffected parents
What can be expected with traits on autosomes (non-sex chrosomes)?
- Expressed in both males and females (affected in roughly equal numbers)
- Both the male and the female parent transmit the trait