Mendelian Genetics My AP Biology Thoughts podcast

My AP Biology Thoughts

Unit 5 Heredity

Welcome to My AP Biology Thoughts podcast, my name is Adrienne Li and I am your host for episode #99 called Unit 5 Heredity: Mendelian Genetics. Today we will be discussing Mendel’s experiment with pea plants, and the three laws he proposed from his results.

Segment 1: Introduction to Mendelian Genetics

First off, lets define what mendelian genetics is. It’s a concept about heredity that was formed by Gregor Mendel and states that genes are distinct units that come in pairs and are inherited independently from other genes. These make up an offspring’s genome and provide the basis of inheritance for sexual reproduction. Now, Mendel didn’t just come up with this concept randomly. It started with an experiment he conducted where he crossbred pure pea plants with different traits such as purple vs. white flowers and tall vs. short stems. The F1 generation all carried the same trait as one of the parents, which refuted the prior notion that inheritance was a blend of the parent’s traits since the flowers weren’t pink. What was more strange was the F2 generation, which had a 3:1 ratio where 3 individuals had the same trait as one parent and 1 individual had the other parent’s trait.

Segment 2: More About Mendelian Genetics

From these experimental results, Mendel summarized his findings in 3 laws. The first one is the law of dominance where genes have two alleles, and the dominant allele will conceal the recessive allele. This was seen in the F1 generation where all the flowers were purple even though one of the parents had white flowers. This meant that purple was dominant while white was recessive, thus only the purple flower trait was expressed. The F2 generation with a 3:1 ratio further confirmed this concept because breeding heterozygotes results in 4 offspring, one that is homozygous dominant, two that are heterozygous, and one that is homozygous recessive which means 3 individuals will express the dominant trait and one will express the recessive trait. Next, the second law is the law of independent assortment which states that alleles of two or more different genes are sorted into gametes independently of another where the allele a gamete receives for one gene does not influence the allele receive for another. This idea was demonstrated when he performed dihybrid crosses which tested two different traits and it resulted in a 9:3:3:1 ratio. This showed that traits such as flower color and stem length are inherited independently from each other, and one does not influence how the other trait is inherited. Lastly, the law of segregation says that during reproduction, the gametes only receive one copy of a gene from each parent at random. This was demonstrated by his 3:1 ratio where during segregation in meiosis of the F1 generation, each gamete acquired one of the two genes so that there were three possible combinations, either homozygous dominant, heterozygous, or homozygous recessive. Since there were two ways to form heterozygotes, either receiving one dominant and one recessive allele from either parent, and because heterozygotes and homozygous dominant gametes express the same phenotype, it supported the 3:1 ratio and law of segregation.

Segment 3: Connection to the Course

Tying this back to the overall ideas in Unit 5, mendelian genetics corroborates the concept of genotypes, phenotypes, and punnett squares. Genotypes are the pairs of alleles that an individual has, such as one purple flower and one white flower allele, whereas phenotypes are the expressed traits which in this example would be a purple flower. This makes sense because of mendelian genetics and the law of dominance, where the dominant allele which is purple flowers, conceals the recessive white flower allele. As for punnett squares, the reason why we can use them to predict mendelian inheritance patterns is because of the law of segregation and independent assortment. The law of segregation allows us to give each gamete one allele from each parent so we can draw an allele in each of the four boxes, and the law of independent assortment allows us to draw alleles independently of one another in dihybrid punnett square crosses since the alleles of one trait are inherited separately from another trait. So that about sums mendelian genetics.

Thank you for listening to this episode of My AP Biology Thoughts. For more student-ran podcasts and digital content, make sure that you visit www.hvspn.com. See you next time bio buddies!

Music Credits:

"Ice Flow" Kevin MacLeod (incompetech.com)
Licensed under Creative Commons: By Attribution 4.0 License
http://creativecommons.org/licenses/by/4.0/

Subscribe to our Podcast

Connect with us on Social Media

Twitter @thehvspn

My AP Biology Thoughts

Unit 5 Heredity

Segment 1: Introduction to Mendelian Genetics

First off, lets define what mendelian genetics is. It’s a concept about heredity that was formed by Gregor Mendel and states that genes are distinct units that come in pairs and are inherited independently from other genes. These make up an offspring’s genome and provide the basis of inheritance for sexual reproduction. Now, Mendel didn’t just come up with this concept randomly. It started with an experiment he conducted where he crossbred pure pea plants with different traits such as purple vs. white flowers and tall vs. short stems. The F1 generation all carried the same trait as one of the parents, which refuted the prior notion that inheritance was a blend of the parent’s traits since the flowers weren’t pink. What was more strange was the F2 generation, which had a 3:1 ratio where 3 individuals had the same trait as one parent and 1 individual had the other parent’s trait.

Segment 2: More About Mendelian Genetics

From these experimental results, Mendel summarized his findings in 3 laws. The first one is the law of dominance where genes have two alleles, and the dominant allele will conceal the recessive allele. This was seen in the F1 generation where all the flowers were purple even though one of the parents had white flowers. This meant that purple was dominant while white was recessive, thus only the purple flower trait was expressed. The F2 generation with a 3:1 ratio further confirmed this concept because breeding heterozygotes results in 4 offspring, one that is homozygous dominant, two that are heterozygous, and one that is homozygous recessive which means 3 individuals will express the dominant trait and one will express the recessive trait. Next, the second law is the law of independent assortment which states that alleles of two or more different genes are sorted into gametes independently of another where the allele a gamete receives for one gene does not influence the allele receive for another. This idea was demonstrated when he performed dihybrid crosses which tested two different traits and it resulted in a 9:3:3:1 ratio. This showed that traits such as flower color and stem length are inherited independently from each other, and one does not influence how the other trait is inherited. Lastly, the law of segregation says that during reproduction, the gametes only receive one copy of a gene from each parent at random. This was demonstrated by his 3:1 ratio where during segregation in meiosis of the F1 generation, each gamete acquired one of the two genes so that there were three possible combinations, either homozygous dominant, heterozygous, or homozygous recessive. Since there were two ways to form heterozygotes, either receiving one dominant and one recessive allele from either parent, and because heterozygotes and homozygous dominant gametes express the same phenotype, it supported the 3:1 ratio and law of segregation.

Segment 3: Connection to the Course

Tying this back to the overall ideas in Unit 5, mendelian genetics corroborates the concept of genotypes, phenotypes, and punnett squares. Genotypes are the pairs of alleles that an individual has, such as one purple flower and one white flower allele, whereas phenotypes are the expressed traits which in this example would be a purple flower. This makes sense because of mendelian genetics and the law of dominance, where the dominant allele which is purple flowers, conceals the recessive white flower allele. As for punnett squares, the reason why we can use them to predict mendelian inheritance patterns is because of the law of segregation and independent assortment. The law of segregation allows us to give each gamete one allele from each parent so we can draw an allele in each of the four boxes, and the law of independent assortment allows us to draw alleles independently of one another in dihybrid punnett square crosses since the alleles of one trait are inherited separately from another trait. So that about sums mendelian genetics.

Thank you for listening to this episode of My AP Biology Thoughts. For more student-ran podcasts and digital content, make sure that you visit www.hvspn.com. See you next time bio buddies!

Music Credits:

"Ice Flow" Kevin MacLeod (incompetech.com)
Licensed under Creative Commons: By Attribution 4.0 License
http://creativecommons.org/licenses/by/4.0/

Subscribe to our Podcast

Connect with us on Social Media

Twitter @thehvspn

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My AP Biology Thoughts « »
Mendelian Genetics

My AP Biology Thoughts

Unit 5 Heredity

Segment 1: Introduction to Mendelian Genetics

Segment 2: More About Mendelian Genetics

Segment 3: Connection to the Course